The minimum wage was $1 in 1956: http://www.infoplease.com/ipa/A0774473.html
Adjusted for inflation that is approximately $8.44 today: http://www.bls.gov/data/inflation_calculator.htm
Per capita GDP was $2,600 in 1956: http://www.measuringworth.com/usgdp/
Adjusted for inflation, that is approximately $21,946 today.
Per capita GDP today is $48,372. Approximately two times greater.
The federal minimum wage today is $7.25.
Thus the minimum wage should be approximately doubled for the increase in per capita GDP.
Minimum wage employees will then be able to spend more to stimulate the economy.
Helping the middle class should start at the bottom.