From Wikipedia:
The earliest snowmobiles were modified Ford Model Ts with the
undercarriage replaced with tracks and skis. They were popular for
rural mail delivery for a time. This early history [1] can be traced
to Carl Eliason [2] in Saynor, Wisconsin with his first hand built
model completed in 1924. He was granted a U.S. patent in 1927.
Polaris Industries in Roseau, Minnesota, in the United States
Midwest, was a pioneer in the production of purpose-built snowmobiles.