Here’s a first person history of the 1st Missouri Engineers. The Clayton men are not listed.

An Illustrated History of the Missouri Engineers and the 25th Infantry Regiments, Together with a roster of both Regiments and the last known addresses that that could be obtained.

Edited by Dr. W. A. Neal, Assistant Surgeon 1st Missouri Engineers, Secretary and Historian of the Society of the 1st Missouri Engineers

1989, Donohue and Henneberry Printers and Binders
Nos. 407-425 Dearborn Street
Chicago, Ill.

https://ia600306.us.archive.org/28/items/illustratedhisto00neal/illustratedhisto00neal.pdf