diff --git a/changelog.d/add-ma-ssp.added.md b/changelog.d/add-ma-ssp.added.md
new file mode 100644
index 00000000000..a51727b5f3e
--- /dev/null
+++ b/changelog.d/add-ma-ssp.added.md
@@ -0,0 +1 @@
+Backdate Massachusetts SSP parameters to 2002.
diff --git a/policyengine_us/parameters/gov/states/ma/dta/ssp/amount.yaml b/policyengine_us/parameters/gov/states/ma/dta/ssp/amount.yaml
index 638491fc2bc..42cf1537e67 100644
--- a/policyengine_us/parameters/gov/states/ma/dta/ssp/amount.yaml
+++ b/policyengine_us/parameters/gov/states/ma/dta/ssp/amount.yaml
@@ -14,96 +14,217 @@ metadata:
   reference:
     - title: 106 CMR, § 327.330 - Payment Standards
       href: https://www.law.cornell.edu/regulations/massachusetts/106-CMR-327-330
+    - title: SSA State Assistance Programs for SSI Recipients, January 2002 - Massachusetts
+      href: https://www.ssa.gov/policy/docs/progdesc/ssi_st_asst/2002/ma.html
+    - title: SSA State Assistance Programs for SSI Recipients, January 2005 - Massachusetts
+      href: https://www.ssa.gov/policy/docs/progdesc/ssi_st_asst/2005/ma.html
+    - title: SSA State Assistance Programs for SSI Recipients, January 2011 - Massachusetts
+      href: https://www.ssa.gov/policy/docs/progdesc/ssi_st_asst/2011/ma.html
     - title: Massachusetts State Supplement Calendar Year 2022 Payment Levels
       href: https://www.mass.gov/doc/federal-and-state-payment-levels-for-calendar-year-cy-2022/download
-    - title: Massachusetts State Supplement Calendar Year 2023 Payment Levels
-      href: https://www.mass.gov/doc/federal-and-state-payment-levels-for-calendar-year-cy-2023/download
-    - title: Massachusetts State Supplement Calendar Year 2024 Payment Levels
-      href: https://www.mass.gov/doc/federal-and-state-payment-levels-for-calendar-year-cy-2024/download
     - title: Massachusetts State Supplement Calendar Year 2025 Payment Levels
       href: https://www.mass.gov/doc/federal-and-state-payment-levels-for-calendar-year-cy-2025/download
 
 FULL_COST:
   AGED:
     1:
-      2022-01-01: 128.82
-    2: 
-      2022-01-01: 100.86
+      2002-01-01: 128.82
+    2:
+      2002-01-01: 100.86
   BLIND:
     1:
-      2022-01-01: 149.74
+      2002-01-01: 149.74
     2:
+      2002-01-01: 286.24
+      2003-01-01: 287.24
+      2004-01-01: 290.74
+      2005-01-01: 294.24
+      2006-01-01: 300.74
+      2007-01-01: 305.74
+      2008-01-01: 308.74
+      2009-01-01: 318.24
+      2012-01-01: 323.74
+      2013-01-01: 326.74
+      2014-01-01: 329.74
+      2015-01-01: 332.74
+      2017-01-01: 333.24
+      2018-01-01: 337.24
+      2019-01-01: 342.24
+      2020-01-01: 345.24
+      2021-01-01: 348.24
       2022-01-01: 360.24
       2023-01-01: 378.24
       2024-01-01: 385.24
       2025-01-01: 391.74
   DISABLED:
     1:
-      2022-01-01: 114.39
+      2002-01-01: 114.39
     2:
-      2022-01-01: 90.03
+      2002-01-01: 90.03
 SHARED_EXPENSES:
   AGED:
     1:
-      2022-01-01: 39.26
-    2: 
-      2022-01-01: 100.86
+      2002-01-01: 39.26
+    2:
+      2002-01-01: 100.86
   BLIND:
     1:
-      2022-01-01: 149.74
+      2002-01-01: 149.74
     2:
+      2002-01-01: 286.24
+      2003-01-01: 287.24
+      2004-01-01: 290.74
+      2005-01-01: 294.24
+      2006-01-01: 300.74
+      2007-01-01: 305.74
+      2008-01-01: 308.74
+      2009-01-01: 318.24
+      2012-01-01: 323.74
+      2013-01-01: 326.74
+      2014-01-01: 329.74
+      2015-01-01: 332.74
+      2017-01-01: 333.24
+      2018-01-01: 337.24
+      2019-01-01: 342.24
+      2020-01-01: 345.24
+      2021-01-01: 348.24
       2022-01-01: 360.24
       2023-01-01: 378.24
       2024-01-01: 385.24
       2025-01-01: 391.74
   DISABLED:
     1:
-      2022-01-01: 30.40
+      2002-01-01: 30.40
     2:
-      2022-01-01: 90.03
+      2002-01-01: 90.03
 HOUSEHOLD_OF_ANOTHER:
   AGED:
     1:
-      2022-01-01: 104.36
+      2002-01-01: 104.36
     2:
-      2022-01-01: 107.90
+      2002-01-01: 107.90
   BLIND:
     1:
+      2002-01-01: 331.40
+      2003-01-01: 333.74
+      2004-01-01: 337.74
+      2005-01-01: 342.74
+      2006-01-01: 350.74
+      2007-01-01: 357.40
+      2008-01-01: 362.07
+      2009-01-01: 374.40
+      2012-01-01: 382.40
+      2013-01-01: 386.40
+      2014-01-01: 390.07
+      2015-01-01: 394.07
+      2017-01-01: 394.74
+      2018-01-01: 399.74
+      2019-01-01: 406.74
+      2020-01-01: 410.74
+      2021-01-01: 414.40
       2022-01-01: 430.07
       2023-01-01: 454.40
       2024-01-01: 464.07
       2025-01-01: 472.07
     2:
+      2002-01-01: 422.40
+      2003-01-01: 425.40
+      2004-01-01: 431.74
+      2005-01-01: 439.07
+      2006-01-01: 451.40
+      2007-01-01: 461.40
+      2008-01-01: 468.07
+      2009-01-01: 486.74
+      2012-01-01: 498.40
+      2013-01-01: 504.40
+      2014-01-01: 510.07
+      2015-01-01: 516.07
+      2017-01-01: 517.07
+      2018-01-01: 524.74
+      2019-01-01: 535.07
+      2020-01-01: 541.07
+      2021-01-01: 546.74
       2022-01-01: 570.40
       2023-01-01: 606.74
       2024-01-01: 621.07
       2025-01-01: 633.40
   DISABLED:
     1:
-      2022-01-01: 87.58
+      2002-01-01: 87.58
     2:
-      2022-01-01: 97.09
+      2002-01-01: 97.09
 REST_HOME:
   AGED:
     1:
-      2022-01-01: 293.00
+      2002-01-01: 293.00
     2:
+      2002-01-01: 429.50
+      2003-01-01: 430.50
+      2004-01-01: 434.00
+      2005-01-01: 437.50
+      2006-01-01: 444.00
+      2007-01-01: 449.00
+      2008-01-01: 452.00
+      2009-01-01: 461.50
+      2012-01-01: 467.00
+      2013-01-01: 470.00
+      2014-01-01: 473.00
+      2015-01-01: 476.00
+      2017-01-01: 476.50
+      2018-01-01: 480.50
+      2019-01-01: 485.50
+      2020-01-01: 488.50
+      2021-01-01: 491.50
       2022-01-01: 503.50
       2023-01-01: 521.50
       2024-01-01: 528.50
       2025-01-01: 535.00
   BLIND:
     1:
-      2022-01-01: 149.74
+      2002-01-01: 149.74
     2:
+      2002-01-01: 286.24
+      2003-01-01: 287.24
+      2004-01-01: 290.74
+      2005-01-01: 294.24
+      2006-01-01: 300.74
+      2007-01-01: 305.74
+      2008-01-01: 308.74
+      2009-01-01: 318.24
+      2012-01-01: 323.74
+      2013-01-01: 326.74
+      2014-01-01: 329.74
+      2015-01-01: 332.74
+      2017-01-01: 333.24
+      2018-01-01: 337.24
+      2019-01-01: 342.24
+      2020-01-01: 345.24
+      2021-01-01: 348.24
       2022-01-01: 360.24
       2023-01-01: 378.24
       2024-01-01: 385.24
       2025-01-01: 391.74
   DISABLED:
     1:
-      2022-01-01: 293.00
+      2002-01-01: 293.00
     2:
+      2002-01-01: 429.50
+      2003-01-01: 430.50
+      2004-01-01: 434.00
+      2005-01-01: 437.50
+      2006-01-01: 444.00
+      2007-01-01: 449.00
+      2008-01-01: 452.00
+      2009-01-01: 461.50
+      2012-01-01: 467.00
+      2013-01-01: 470.00
+      2014-01-01: 473.00
+      2015-01-01: 476.00
+      2017-01-01: 476.50
+      2018-01-01: 480.50
+      2019-01-01: 485.50
+      2020-01-01: 488.50
+      2021-01-01: 491.50
       2022-01-01: 503.50
       2023-01-01: 521.50
       2024-01-01: 528.50
@@ -111,32 +232,38 @@ REST_HOME:
 MEDICAID_FACILITY:
   AGED:
     1:
-      2022-01-01: 42.80
+      2002-01-01: 35.00
+      2008-01-01: 42.80
     2:
-      2022-01-01: 42.80
+      2002-01-01: 35.00
+      2008-01-01: 42.80
   BLIND:
     1:
-      2022-01-01: 42.80
+      2002-01-01: 35.00
+      2008-01-01: 42.80
     2:
-      2022-01-01: 42.80
+      2002-01-01: 35.00
+      2008-01-01: 42.80
   DISABLED:
     1:
-      2022-01-01: 42.80
+      2002-01-01: 35.00
+      2008-01-01: 42.80
     2:
-      2022-01-01: 42.80
+      2002-01-01: 35.00
+      2008-01-01: 42.80
 ASSISTED_LIVING:
   AGED:
     1:
-      2022-01-01: 454.00
+      2002-01-01: 454.00
     2:
-      2022-01-01: 340.50
+      2002-01-01: 340.50
   BLIND:
     1:
-      2022-01-01: 454.00
+      2002-01-01: 454.00
     2:
-      2022-01-01: 340.50
+      2002-01-01: 340.50
   DISABLED:
     1:
-      2022-01-01: 454.00
+      2002-01-01: 454.00
     2:
-      2022-01-01: 340.50
+      2002-01-01: 340.50
diff --git a/policyengine_us/tests/policy/baseline/gov/states/ma/dta/ssp/ma_maximum_state_supplement.yaml b/policyengine_us/tests/policy/baseline/gov/states/ma/dta/ssp/ma_maximum_state_supplement.yaml
index c174a95bdfa..5f5656b7e60 100644
--- a/policyengine_us/tests/policy/baseline/gov/states/ma/dta/ssp/ma_maximum_state_supplement.yaml
+++ b/policyengine_us/tests/policy/baseline/gov/states/ma/dta/ssp/ma_maximum_state_supplement.yaml
@@ -1,14 +1,7 @@
-# File: policyengine_us/tests/policy/baseline/gov/ssa/state_supplement/maximum_state_supplement.yaml
-# Explanation:
-#   - We explicitly mark each person as SSI-eligible by setting:
-#       is_ssi_eligible: true
-#       meets_ssi_resource_test: true
-#       is_ssi_aged_blind_disabled: true
-#       (and the appropriate is_blind / is_disabled / is_ssi_aged)
-#   - This ensures that maximum_state_supplement doesn't return 0 due to the 'defined_for' condition.
-#   - Use numeric underscores for readability (like 1_373, 2_767, etc.).
+# Tests for ma_maximum_state_supplement across different living arrangements,
+# categories, and historical periods.
 
-- name: Single disabled, FULL_COST
+- name: Case 1, single disabled, FULL_COST, 2022.
   period: 2022
   absolute_error_margin: 1
   input:
@@ -17,10 +10,8 @@
         age: 30
         is_disabled: true
         is_tax_unit_spouse: false
-        # needed for maximum_state_supplement to not be 0:
         meets_ssi_resource_test: true
         is_ssi_eligible: true
-        # ensures the person is recognized as ABD (Aged/Blind/Disabled):
         is_ssi_aged_blind_disabled: true
     households:
       household:
@@ -31,10 +22,9 @@
       unit:
         members: [person_disabled]
   output:
-    # Suppose p["MA"]["FULL_COST"]["DISABLED"]["1"] = 114.39 monthly => ~1373 annual
     ma_maximum_state_supplement: 1_373
 
-- name: Couple both aged, FULL_COST
+- name: Case 2, couple both aged, FULL_COST, 2022.
   period: 2022
   absolute_error_margin: 1
   input:
@@ -62,11 +52,9 @@
       unit:
         members: [spouse1, spouse2]
   output:
-    # Suppose p["MA"]["FULL_COST"]["AGED"]["2"] => 100.86 monthly each => ~1_210 annual each
-    # => final = [1_210, 1_210]
     ma_maximum_state_supplement: [1_210, 1_210]
 
-- name: One aged, one blind, FULL_COST
+- name: Case 3, one aged one blind, FULL_COST, 2022.
   period: 2022
   absolute_error_margin: 1
   input:
@@ -94,8 +82,172 @@
       unit:
         members: [person_1, person_2]
   output:
-    # p["MA"]["FULL_COST"]["AGED"]["2"] might be 100.86 monthly => ~1_210 each for the aged spouse
-    # p["MA"]["FULL_COST"]["BLIND"]["2"] might be 360.24 monthly => ~4_323 each for the blind spouse
-    # The code's logic is 'max_()' for each person, so spouse1 gets 1_210, spouse2 gets 4_323,
-    # but the code then sums them up and divides by 2 => ~2_766 each. We'll guess ~[2_766, 2_766].
     ma_maximum_state_supplement: [2_766, 2_766]
+
+- name: Case 4, single blind, FULL_COST, 2005.
+  period: 2005
+  absolute_error_margin: 1
+  input:
+    people:
+      person_blind:
+        age: 35
+        is_blind: true
+        is_tax_unit_spouse: false
+        meets_ssi_resource_test: true
+        is_ssi_eligible: true
+        is_ssi_aged_blind_disabled: true
+    households:
+      household:
+        members: [person_blind]
+        state_code: MA
+        ma_state_living_arrangement: FULL_COST
+    marital_units:
+      unit:
+        members: [person_blind]
+  output:
+    # 149.74 * 12 = 1796.88
+    ma_maximum_state_supplement: 1_797
+
+- name: Case 5, single aged, HOUSEHOLD_OF_ANOTHER, 2002.
+  period: 2002
+  absolute_error_margin: 1
+  input:
+    people:
+      person_aged:
+        age: 70
+        is_tax_unit_spouse: false
+        meets_ssi_resource_test: true
+        is_ssi_eligible: true
+        is_ssi_aged_blind_disabled: true
+        is_ssi_aged: true
+    households:
+      household:
+        members: [person_aged]
+        state_code: MA
+        ma_state_living_arrangement: HOUSEHOLD_OF_ANOTHER
+    marital_units:
+      unit:
+        members: [person_aged]
+  output:
+    # 104.36 * 12 = 1252.32
+    ma_maximum_state_supplement: 1_252
+
+- name: Case 6, single disabled, REST_HOME, 2009.
+  period: 2009
+  absolute_error_margin: 1
+  input:
+    people:
+      person_disabled:
+        age: 45
+        is_disabled: true
+        is_tax_unit_spouse: false
+        meets_ssi_resource_test: true
+        is_ssi_eligible: true
+        is_ssi_aged_blind_disabled: true
+    households:
+      household:
+        members: [person_disabled]
+        state_code: MA
+        ma_state_living_arrangement: REST_HOME
+    marital_units:
+      unit:
+        members: [person_disabled]
+  output:
+    # 293 * 12 = 3516
+    ma_maximum_state_supplement: 3_516
+
+- name: Case 7, single aged, MEDICAID_FACILITY, 2005.
+  period: 2005
+  absolute_error_margin: 1
+  input:
+    people:
+      person_aged:
+        age: 72
+        is_tax_unit_spouse: false
+        meets_ssi_resource_test: true
+        is_ssi_eligible: true
+        is_ssi_aged_blind_disabled: true
+        is_ssi_aged: true
+    households:
+      household:
+        members: [person_aged]
+        state_code: MA
+        ma_state_living_arrangement: MEDICAID_FACILITY
+    marital_units:
+      unit:
+        members: [person_aged]
+  output:
+    # 35.00 * 12 = 420
+    ma_maximum_state_supplement: 420
+
+- name: Case 8, single aged, MEDICAID_FACILITY, 2009.
+  period: 2009
+  absolute_error_margin: 1
+  input:
+    people:
+      person_aged:
+        age: 72
+        is_tax_unit_spouse: false
+        meets_ssi_resource_test: true
+        is_ssi_eligible: true
+        is_ssi_aged_blind_disabled: true
+        is_ssi_aged: true
+    households:
+      household:
+        members: [person_aged]
+        state_code: MA
+        ma_state_living_arrangement: MEDICAID_FACILITY
+    marital_units:
+      unit:
+        members: [person_aged]
+  output:
+    # 42.80 * 12 = 513.60
+    ma_maximum_state_supplement: 514
+
+- name: Case 9, single disabled, ASSISTED_LIVING, 2002.
+  period: 2002
+  absolute_error_margin: 1
+  input:
+    people:
+      person_disabled:
+        age: 50
+        is_disabled: true
+        is_tax_unit_spouse: false
+        meets_ssi_resource_test: true
+        is_ssi_eligible: true
+        is_ssi_aged_blind_disabled: true
+    households:
+      household:
+        members: [person_disabled]
+        state_code: MA
+        ma_state_living_arrangement: ASSISTED_LIVING
+    marital_units:
+      unit:
+        members: [person_disabled]
+  output:
+    # 454 * 12 = 5448
+    ma_maximum_state_supplement: 5_448
+
+- name: Case 10, single blind, HOUSEHOLD_OF_ANOTHER, 2011.
+  period: 2011
+  absolute_error_margin: 1
+  input:
+    people:
+      person_blind:
+        age: 40
+        is_blind: true
+        is_tax_unit_spouse: false
+        meets_ssi_resource_test: true
+        is_ssi_eligible: true
+        is_ssi_aged_blind_disabled: true
+    households:
+      household:
+        members: [person_blind]
+        state_code: MA
+        ma_state_living_arrangement: HOUSEHOLD_OF_ANOTHER
+    marital_units:
+      unit:
+        members: [person_blind]
+  output:
+    # 374.40 * 12 = 4492.80
+    ma_maximum_state_supplement: 4_493