In 1852, Rev. Freeman became the pastor of Siloam Presbyterian Church in Brooklyn, New York, founded in 1849. He served there from 1852 to 1860. He was a longtime friend of Amos Gerry Beman, a prominent black minister active in the Northeast. In 1853, he was a prominent attendee of the radical abolitionist National African American Convention in Rochester, New York. His was one of 5 names attached to the address of the convention to the people of the United States published under the title, "The Claims of Our Common Cause", along with Frederick Douglass, James Monroe Whitfield, Henry O. Wagoner, and George Boyer Vashon. In 1857 Freeman moderated the annual meeting of the Evangelical Association of Colored Ministers of Congregational and Presbyterian Churches, which met from 1856 to 1859 to confirm their distinctive vocation; that year they met at the Central Presbyterian Church in Philadelphia. In 1859 Freeman hosted this meeting at the Siloam Church, by which time there were 27 black churches in the group.