Reason's first teaching job, in the 1830s, was at "the Quaker school in Laurens Street." In 1847, Reason, along with
Charles Bennett Ray, founded the New York-based Society for the Promotion of Education among Colored Children. Two years later, he was appointed professor of
belles-lettres,
Greek,
Latin, and
French at
New York Central College, McGrawville, while also serving as an
adjunct professor of mathematics. Central College was the first college to be integrated from its opening day; it hired Reason as the most qualified applicant. Reason was thus both the first Black professor, and the first Black teacher with white students, in the United States. Reason returned to New York, where he served for decades in
public education as a teacher, administrator, and reformer. He was principal of Colored Grammar School No. 3, at 78 West 40th Street. Later he was principal of Colored School No. 6 on 36th Street. During this time, he was instrumental in efforts to abolish
slavery and
segregation. He was a delegate to the
Colored Labor Convention held in
Saratoga Springs, New York, in 1870. In 1878, he owned a
brownstone at 242 East 53rd St. It was filled with books. He was described as "a remarkably well-read man and speaks several languages. ...He is said to be worth $60,000" (). ==Marriage and family==