25. James Simons
Simons was a math professor at Massachusetts Institute of Technology, his alma mater, and at Harvard, before eventually becoming chair of the math department at Stony Brook University. Simons left academia in 1982 to start Renaissance Technologies, a quantitative-trading firm that eventually spawned the most successful hedge fund ever. Simons, who retired in 2010, continues to promote math in the classroom as founder and chairman of Math for America, a program that helps train STEM teachers and supports them with stipends.