After Democrats regained power in the state legislature following Reconstruction, in 1890 they disenfranchised most blacks in the state (who were a majority of the population) by a new constitution that raised barriers to voter registration. Then in his 50s, Lynch studied law; he was admitted to the Mississippi bar in 1896. Seeing the effects of disenfranchisement, Lynch left the state and returned to Washington, DC to practice law. He served in the United States Army during the Spanish–American War and for a decade into the early 1900s, achieving the rank of major. After retiring, Lynch moved to Chicago, Illinois, where he lived for more than two decades. After his military service, Lynch was active in law and real estate in Chicago.