This is a large genus in the Acroneuriinae subfamily that currently contains 24 species. Distribution is primarily southern though a few species make it into the East and Midwest. Perlesta placida is reportedly a common species. Only a single western species of limited importance and distribution is known for the southern Rockies.
I don't know why "Stoneflies of the United States" has such a limited range for Perlesta placida, but we (Madmen Chapter of TU) have collected them on the Mad River, Logan Co., OH. They were reported by Gaufin (1956, Ohio J. Sci. 56 (6):321-324) in numerous counties. They have been recorded more recently by Ohio EPA.