Promoted in the Army to Brevet Second Lieutenant, 1st Infantry Regiment serving at his first post at Fort Snelling, from 1843 to 1846.
[1] He was assigned to the garrison at East Pascagoula, Mississippi in 1848, then on frontier duty at Fort Washita, Indian Territory from 1848 to 1851.
[2] Selden returned to Texas frontier duty at Fort McIntosh, from 1854 to 1855 and Ringgold Barracks in 1855, serving as Adjutant, 5th Infantry, from May 1 to October 18, 1855.
[1][3] With the secession crisis in New Mexico Territory, resulting in the formation of Confederate Arizona, Selden was sent to command and defend Fort Craig with five companies of the 5th Infantry Regiment from August 14, 1861, to January 31, 1862.
Fort Craig blocked the approach to Union held New Mexico from Confederate Arizona up the Rio Grande or Jornada del Muerto.
[1] He was first buried at Fort Union, and when that post was closed his grave was moved to Santa Fe National Cemetery.