Check out ebay - you'll be surprised how many people sell old maps. I was looking for maps of the Caribbean for our pirate campaign and the question wasn't I would be able to find one or not, it was what timeframe I wanted the map to be.
You can see that Utah became a state sometime between the two elections, leaving Arizona, New Mexico, and Oklahoma as the only territories in the "lower 48".
Alaska was also still a territory at the time and going through a bit of a gold rush. The U.S. fought the Spanish-American War around this time and took Puerto Rico, Guam and the Phillipines as colonies. The U.S. also got a hold of Hawaii at about the same time. We were able to engage in these overseas "adventures" because the constant internal "Indian Wars" had largely been won (or lost depending on your point of view) by the end of the 1880's.
Try Googling the U.S. census beaureu for info on demographics and population.