In 1885, at age 27, he moved to
Windsor, Colorado, either in search of better health, wrote
Aven Nelson, or to pursue a strong desire to study Rocky Mountain plants, inspired by one of his college professors, according to
Roger Lawrence Williams. He established a lumber business in Windsor, and resided there for the rest of his life, "where he was known as a successful business man, a kindly neighbor, a philanthropic Christian, a scientist of more than local renown." He consulted with professional botanists, especially Aven Nelson of the
University of Wyoming, and
Per Axel Rydberg. His personal herbarium grew to over 20,000 specimen sheets. Of these, 8,330 were of his own collections, and described by
Roger Lawrence Williams as "testimony to leisure time arduously spent." The others Osterhout acquired via trading or purchase. Upon his death, all of his sheets were bequeathed to the Rocky Mountain Herbarium. According to IPNI, his botanical author abbreviation,
Osterh., is associated with 237 plant names or historical variations theron. His nomenclatural efforts appear within his 44 publications, as listed by Roger Williams, which also includes two essays on Rocky Mountain botanizing, one a commemoration of the 100th anniversary of the first major botanical exploration of the Rocky Mountains in 1820 (as described in an account by
Edwin James). == Plants named in Osterhout's honor ==