after his term expired, isham spent two years in europe, then returned to his law practice. in february 1872, isham admitted robert todd lincoln, the son of abraham lincoln, as a junior partner. in 1886, william g. beale was also admitted as a partner, and henceforth the partnership was known as isham lincoln & beale. the firm retained this name until it dissolved in 1988. isham's most notable cases include the arrangement of the walter loomis newberry library endowment and the 1875 mayoral election controversy between harvey doolittle colvin & monroe heath. he received an ll.d. from williams college in 1893.