Yes, United States stopped using penal labor at twentieth (http://en.wikipedia.org/wiki/Penal_labour#United_States). Soviet Union at fifties.
I think 30 years lag is not soo bad considering level of social-economic development of USSR and USA.
Penal labor is extremely prevalent in the US, and if anything, is growing (over 1 million US prisoners today are engaged in penal labor).
It might not be "punative" penal labor, which takes it out of the category of "forced labor." But US prisoners do labor in private prisons for private companies, with the sole remuneration of reducing time from their sentences.
I still think that cutting wood or digging ore in Siberia (see e.g. the weather in the fine city of Norilsk) is noticeably more cruel than serving time in a US prison. A quick googling allows me to assume that forced labor as a punishment has not been used in the US since 1940s, except for rare cases in the military.
I very much hope the the US government, however crooked it might be, is not considering high incarceration level as an engine of economic growth.