The Social Security Act was passed in 1935. Benefits did not begin until two years later. What were those benefits?
From 1937 until 1940, Social Security paid benefits in the form of a single, lump-sum payment...The average lump-sum payment during this period was $58.06.
The Act as originally written had many imperfections:
Job categories that were not covered by the act included workers in agricultural labor, domestic service, government employees, and many teachers, nurses, hospital employees, librarians, and social workers.[12] The act also denied coverage to individuals who worked intermittently.[13] These jobs were dominated by women and minorities. For example, women made up 90% of domestic labor in 1940 and two-thirds of all employed black women were in domestic service.[14] Exclusions exempted nearly half the working population.
At first, monthly benefits were not set to begin until 1942, but in 1939 the Act was amended to move the starting date of those monthly payments up to 1940:
On January 31, 1940, the first monthly retirement check was issued to Ida May Fuller of Ludlow, Vermont, in the amount of $22.54. Miss Fuller, a Legal Secretary, retired in November 1939.
It was in this same year that widows and dependent children became eligible for benefits. They had previously been excluded.
The program remained virtually unchanged for the next ten years. Then, in 1950, the first COLA, or cost of living allowance, was added:
It was not until the 1950 Amendments that Congress first legislated an increase in benefits. Current beneficiaries had their payments recomputed and Ida May Fuller, for example, saw her monthly check increase from $22.54 to $41.30.
COLAs remained intermittent for the next quarter century, and it wasn't until the 1970s that they became a permanent annual feature.
The next major amendment was in 1954:
The Social Security Amendments of 1954 initiated a disability insurance program which provided the public with additional coverage against economic insecurity. At first, there was a disability "freeze" of a worker's Social Security record during the years when they were unable to work...While this measure offered no cash benefits, it did prevent such periods of disability from reducing or wiping out retirement and survivor benefits.
This was again amended in 1960:
In September 1960 President Eisenhower signed a law amending the disability rules to permit payment of benefits to disabled workers of any age and to their dependents.
Perhaps the biggest change of all occurred in 1965, with the passage of Medicare:
With the signing of this bill, SSA became responsible for administering a new social insurance program that extended health coverage to almost all Americans aged 65 or older. Nearly 20 million beneficiaries enrolled in Medicare in the first 3 years of the program.
There weren't any other major changes until the mid-'70s, with the addition of COLAs, already noted above. In summary, Social Security took roughly 40 years to take the form in which we know it today.
Note: this diarist in no way endorses the idea that major legislation ought to start out crappy and inadequate and take four decades to be fixed.