On September 16, 1840, in Jacksonville, Alabama, Erasmus married Lucy Ann Morgan (October 22, 1821 – c. 1887), the daughter of George Washington Morgan and Mary Frances Irby. By 1845 he was practicing medicine in Oktibbeha County, Mississippi, and became a member of the House of Representatives representing Oktibbeha County, and State Auditor. While chairman of the Committee on Claims and a member of the Committee of Education he was instrumental in founding the Mississippi Institution for the Education of the Deaf and Dumb in 1854.