Montana created twenty-six counties during its 1910 county-splitting craze. Among them was Big Horn County, carved from portions of Yellowstone and Rosebud Counties in 1913. Private entrepreneurs constructed the new county’s first courthouses. In 1913, the county leased offices in the Sullivan Block. In 1918, W. O. Lee won the contract “to furnish 20 rooms for courthouse purposes.” To fulfill the contract, he hired Percy Wilcox to construct this $60,000, two-story building. The Prairie style likely inspired the handsome building’s geometric decoration, bands of windows, and horizontal emphasis. Sibley Drug Store and Stockman Bank shared the business block with the county. The bank personalized its interior with mahogany wainscoting, marble trim, and a marble floor. In 1923 the bank closed, a victim of the agricultural depression. That year, the county also moved its offices back to the Sullivan Block. A post office, a clothing store, and a dance hall (on the second floor in the former courtroom) were among the building’s later occupants. The Wilson Building sign dates from the 1960s or 1970s, when Judge Robert Wilson owned the property.