John Maclean Sr. (1771-1814) was the College of New Jersey’s first chemistry professor and a slaveholder. His son John Maclean Jr. (1800-1886) would serve as Princeton's president from 1854 to 1868. Maclean Sr., a trained physician, arrived in the United States from Scotland in 1795 and began teaching at the college that year. During his tenure at Princeton from 1795 to 1812, Maclean was a professor of science and mathematics as well as bursar and clerk for President Samuel Stanhope Smith. In 1798, Maclean declared his intentions to become a U.S. citizen and married Phoebe Bainbridge of New York.
In the first days of January 1799, Maclean purchased an enslaved woman named Lydia for the sum of $160. As with so many historical records about enslaved people, this bill of sale—the only extant piece of information about Lydia's life in Maclean's household—leaves many questions and silences about her experiences.