Here is a short (15 page) history of the Social Security Program (from the social security administration) which I think has some worthwhile background info. It's at:
I think it is interesting that two of the biggest expansions of the program, which are partially driving the solvency concerns, were passed as recently as the 1970's: a 20% increase in benefits and making the cost of living adjustments automatic and indexed to the cpi for wages. Now certainly that's 30+ years ago, which represents the working life of many people. However, it diminishes the arguments of opponents to reform that SS has always been there for retirees since FDR and now any suggested reforms are changing the deal. In fact, the program has evolved/changed significantly over the years.