What were the two cornerstone pieces of the New Deal legislation that were most important for African Americans?
For the most part, the New Deal was not very friendly to African Americans. Many programs discriminated against African Americans and some, like the AAA, actively hurt them. However, there were some programs that did more than others to help them.
For example, the WPA did do a fair amount for African Americans. The link below tells us that this program taught many African Americans to read and write. The program also paid many blacks to do various sorts of work, even if it did pay them less than it paid whites. The same was true for the CCC, which employed many young blacks, again in segregated units. Overall, then, I would argue that these two New Deal programs were the most important for African Americans.