Princeton, Fordham University, and Union College later each gave him the honorary degree of Doctor of Laws.

In 1892, McClellan was elected president of the Board of Aldermen of New York City for the following two years, and for a part of 1894 he served as acting mayor.

While in Congress he strongly opposed the war with Spain in 1898, and supported President McKinley's efforts to find a compromise.

[3] In November 1903, McClellan defeated the sitting mayor, Seth Low (independent Fusion), for a two-year term.

[clarification needed] He is notable in the history of movie censorship for canceling all moving-picture exhibition licenses on Christmas Eve 1908, claiming that the new medium degraded the morals of the community and that celluloid film was an unacceptable fire hazard.

Throughout his political career, McClellan remained interested in education and in 1906 he was named honorary Chancellor of Union College.