He was the son of U.S. Army officer Silas Casey, so his family moved along with his father's changing military assignments.

After the outbreak of the American Civil War, he was promoted to master on 31 August 1861 and participated in an engagement with the shore batteries at Pensacola, Florida in October 1861.

Promoted to lieutenant effective 16 July 1862, Casey served as executive officer of the gunboat USS Wissahickon in the South Atlantic Blockading Squadron from 1862 to 1863.

He participated in several engagements with Fort McAllister at Savannah, Georgia in 1862 and the first naval attack on Charleston, South Carolina in April 1863.

[2][4] From 1870 to 1873, Casey served as executive officer on the screw frigate USS Colorado, which was the flagship of Rear Adm. John Rodgers in the Asiatic Squadron.

From 1884 to 1889, Casey was inspector for the Fifth Lighthouse District and commander of the receiving ship USS Dale at the Washington Navy Yard.

[3] In July 1890, he was assigned to the fitting out of the protected cruiser USS Newark and then served as her first commanding officer from February 1891 to May 1893.

From April 1894 to February 1897, Casey was commanding officer of the receiving ship USS Vermont at the New York Navy Yard.