Cleveland worked for the Rogers firm for three years, then left in 1862 to start his own practice. In January 1863, he was appointed assistant district attorney of Erie County. With the American Civil War raging, Congress passed the Conscription Act of 1863, requiring able-bodied men to serve in the army if called upon, or else to hire a substitute. Cleveland chose the latter course, paying $150 (equivalent to $3,115 in 2019) to George Benninsky, a thirty-two-year-old Polish immigrant, to serve in his place. Benninsky survived the war.