After his return to the U.S. in 1919, he entered Harvard Law School. He was the first black student elected to the editorial board of the "Harvard Law Review" and graduated "cum laude". Houston was also a member of Alpha Phi Alpha fraternity. He earned a bachelor's of law in 1922 and a JD from Harvard in 1923. That same year he was awarded a Sheldon Traveling Fellowship to study at the University of Madrid. After his return, he was admitted to the Washington, DC bar in 1924 and joined his father's practice.