Complex sentence: Garnet served as the pastor of the Liberty (Fifteenth) Street Presbyterian Church from 1864 until 1866, and during this time he became the first black minister to preach to the House of Representatives, on 12 February 1865.
Split into simpler sentences: Garnet served as the pastor of the Liberty (Fifteenth) Street Presbyterian Church from 1864 until 1866. During this time he became the first black minister to preach to the House of Representatives, on 12 February 1865.