Plumer was the minister of several churches during his career, most notably: First Presbyterian Church,
Richmond, Virginia (1834–1846);
Franklin Street Presbyterian Church,
Baltimore, Maryland (1847–1854); Central Presbyterian Church,
Allegheny, Pennsylvania (1854–1862);
Arch Street Presbyterian Church,
Philadelphia, Pennsylvania (1862–1865); and Second Presbyterian Church,
Pottsville, Pennsylvania (1865–1867). From 1837 to 1845 Plumer was the editor of
The Watchman of the South, a weekly Presbyterian newspaper which he had founded while serving as pastor in Richmond. He was also a founder of
Staunton's Institution for the Blind, Deaf, & Dumb. Plumer moderated the General Assemblies of two different sects of American Presbyterianism, one in the
Presbyterian Church of the United States of America in 1838 and in the
Presbyterian Church in the United States in 1871. In both institutions he was a staunch supporter of
Old School Presbyterianism. ==Career as educator==