He further continued his education in Drury College at Springfield, Missouri, which conferred upon him a Master of Science degree in 1890.

[3][4] At that time he started to curate and edit large duplicate series of herbarium specimens with printed labels and fixed titles, among others Plants of Wyoming.

From the Rocky Mountain Herbarium and Plants of Yellowstone National Park.

In 1931, he married fellow botanist Ruth Elizabeth Ashton (1896-1987) in Santa Fe, New Mexico.

The Aven Nelson Memorial Building on the campus of the University of Wyoming is named in his honor.