As you probably know
stuey, the Custer fight was on the Little Big Horn river, just outside of present day Hardin, Montana, (actually Crow Agency, which is on the Crow Indian Reservation) in extreme southern Montana (spit on a windy day and it'll land in Wyoming). We're about 80-90 miles south of there as the crow (no pun intended) flies.
You can Google the Fetterman Battle (December 21, 1866) and find that one occurred some 10 years previous to Custer (June 25, 1876) and was actually more significant historically since the end result was the total defeat of and abandonment by the U.S. Army from 3 forts located along the Bozeman Trail and a complete withdrawal from the area, which relenquished the wagon route to the combined Sioux/Arapaho/Cheyenne tribes for another 10 years or so.
Fetterman, like Custer resulted in the deaths of all in both commands... some 268 or so in Custer's and 81 in Fetterman's command. For a painting of the Fetterman fight, go here:
http://www.philkearny.vcn.com/fettermanfight.htm ...
Both of these (and others) are in what is known as the Powder River Basin which drains enormous numbers of square miles in Wyoming and Montana... The Powder River is known for being "a mile wide and an inch deep... to wet to walk on to muddy to drink"... The area is still largely unpopulated today...