On March 18, 1818, the US Congress approved the first pensions for government service. The entire article is somewhat long, but it is quite an interesting look into military pensions up until 1890. From the article:
"Class II.
Pensions of the second class were first granted nearly thirty-five years after the close of the Revolution, by the act of March 18, 1818, which provided that every officer, soldier, sailor, and marine who served nine months in the Revolution, and who was or should become in need of assistance from his country for support, should be pensioned for life, officers at *20 per month, and enlisted men at $8. There was no further legislation of this general character until the act of June 27, 1890, which grants to the widow of every officer and enlisted man who served ninety days or more in the war of the rebellion a pension of $8 per month, with *2 additional for each child of the soldier under sixteen years of age, in case she is without other means of support than her daily labor. When the widow dies or remarries, the right survives to the minor children, as under former laws, and pension is continued during life to children who are insane, idiotic, or otherwise permanently helpless."