Where did they go and did they see combat? I am asking because I am researching Whitcomb L. Judson, the guy who is credited with the invention of the zipper, and i have seen multiple references to his enlisting with the 42 Illinois Cavalry in 1861.
The Illinois Secretary of State official Civil War muster rolls website, as well as this website, and wikipedia's page on Illinois Civil War units show that there was no "42nd Illinois Cavalry."
Whitcomb Judson was listed as being a member of C Company, 42nd Illinois Volunteer Infantry, joining August 10th, 1861 at Camp Douglas. The 42nd Illinois was formed in July of 1861, and marched out for St Louis in September. It wintered nearby, and did not participate in any action of note until Feb 28th, 1862, against New Madrid.
You can find a Regimental History of the 42nd Illinois here.
Judson survived the war, and left the 42nd in 1865.