[2] Crounse established a law practice at Fort Plain, New York.During the Civil War he organized Battery K, New York Light Artillery and became a captain in 1861, served for a year; but was discharged after suffering wounds at a battle on the Rappahannock River in Virginia and resumed his law practice.He became a Justice of Nebraska state supreme court from 1867 to 1873, and after his term expired, ran and was elected as a Republican to the Forty-third and Forty-fourth Congresses (1873–1877).He became an internal revenue collector for the district of Nebraska in 1879, and then was appointed Assistant Secretary of the United States Treasury on April 27, 1891.During his term, future Nebraska representative William E. Andrews worked as his private secretary.