richardson was born in fairfax, vermont. he was reportedly a descendant of famed american revolutionary war general israel putnam. he was appointed from vermont to the united states military academy in west point, new york. he graduated 38th out of 52 cadets in the class of 1841. he was one of 23 classmates who would become generals during the civil war. after some routine assignments, richardson served as a second lieutenant in the second seminole war in florida. he was promoted to first lieutenant on sep 21, 1846.