I found a transcription on the Internet of a presidential letter about House Bill No. 4797: "An act granting a pension for Robert H. Stapleton". This 1886 bill came before President Grover Cleveland to sign. Although it appears that Stapleton was injured during the Battle of Valverde on 21 February 1862, Cleveland vetoed the pension request because it was made after the 4 July 1874 deadline.
I find it interesting that the U.S. Congress and the President of the United States would spend the time to vote on and veto a bill on a pension for a New Mexican lieutenant colonel. I guess they didn't have much to do at the time.
Stackpole was married to Maria Paubla Baca, a daughter of my fourth great-grandmother Maria Guadalupe Torres.