In 1833, he was invited by the botanist Thomas Nuttall to join him on Nathaniel Jarvis Wyeth's second expedition across the Rocky Mountains to the Pacific Ocean.

His sister Mary, a naturalist with an interest in entomology, wrote a popular book called "Life In the Insect World" in 1844.

[6] This occurred when the post's gunsmith, Thomas J. Hubbard, attacked and killed the fort's tailor in an argument over a young native girl.

[7][8] On his return, Townsend wrote The Narrative of a Journey across the Rocky Mountains to the Columbia River and a Visit to the Sandwich Islands (1839).

Townsend's ground squirrel (Spermophilus townsendii) is endemic to the southwestern region of the state of Washington.

[7] The whitetail jackrabbit (Lepus townsendii) ranges through southern Canada and the western, central US through eastern California and Colorado.