He was in private practice in Stromsburg, Nebraska from 1890 to 1893, and in Tacoma, Washington from 1893 to 1900.
He was an Assistant United States Attorney for the District of Washington from 1900 to 1904, and was a special assistant to the United States Attorney General for the Ninth Judicial Circuit from 1904 to 1909.
[1] On April 9, 1912, Cushman was nominated by President William Howard Taft to a seat on the United States District Court for the Western District of Washington vacated by Judge George Donworth.
Cushman was confirmed by the United States Senate on May 1, 1912, and received his commission the same day.
He assumed senior status on November 3, 1939, serving in that capacity until his death on January 25, 1944, in Tacoma.