mcclintock matriculated at wesleyan university in middletown, connecticut. ill health, however, forced him to leave wesleyan in his freshman year. unable to return, he graduated subsequently from the university of pennsylvania in 1835, and was assistant professor of mathematics (1836–1837), professor of mathematics (1837–1840), and professor of latin and greek (1840–1848) in dickinson college, carlisle, pennsylvania. he opposed the mexican–american war, as well as slavery, but did not consider himself an abolitionist. in 1847 mcclintock was arrested on the charge of instigating a riot, which resulted in the rescue of several fugitive slaves; his trial, in which he was acquitted, attracted wide attention. the trial dealt with the issue of personal liberty laws in the north and the fugitive slave crisis.