File:101 E Main - Bozeman Montana - 2013-07-09.jpg

English: The Willson Building (101 E. Main Street), in Bozeman, Montana.

It was constructed in 1903 by Lester Willson. Willson was born in Canton, New York, in 1839. Graduating from public school in 1895, he worked as a clerk until enlisting in Company A, 60th New York Volunteers in August 1861. He rose quickly through the ranks, becoming a lieutenant in October 1862, a captain in August 1864, a lieutenant colonel two months later, and a colonel in May 17, 1865. Although he had already left military service, he was brevetted to Brigadier General of Volunteers in 1867. That same year, he followed his brother Davis to Bozeman, arriving in May. He joined his brother and two other men in running a mercantile business. He married, and then when Davis and the other investors dropped out he was left running what was now called "The Willson Company" until his death. He also sat on the very first board of trustees of Montana State University, and founded Gallatin Valley National Bank. He co-founded the Montana Republican Party, and he won a seat in the Montana Territorial Legislature in 1868. He built a home at 504 Central Avenue (which was renamed Willson Avenue after his death), and it stands to this day. Lester Willson died on January 26, 1919. His only surviving adult child, Fred Willson, became the most prominent architect in Bozeman history -- designing most of downtown.

The Willson Company department store occupied it until 1949. Afterward, a variety of retail stores operated in it.

Although the structure is located within the Main Street Historic District, which is listed on the National Register of Historic Places, it is not a contributing structure.