Fire cleared this site in 1824, and the Old Mill rose on it in 1825 as UVM's oldest campus building, along the central-eastern side of the University Green in Burlington. The structure you see was constructed in 1825 on the very site of its predecessor, which had burned in 1824. The original Main College had been raised in 1801–02 by architect and master builder John Johnson, who also designed this replacement.
On April 26, 1825 Vermont Governor Cornelius P. Van Ness laid the cornerstone for North College; two months later, on June 29, General Lafayette laid the cornerstone for South College during his national tour. In 1825 the Main College consisted of two three-story buildings, each 75 by 36 feet, known as North and South Colleges. A third three-story building, 86 feet long and called Middle College, was added between them in 1829.
Each building sat about seven to eight feet apart to prevent fire from consuming the whole complex, a direct response to the 1824 blaze; in 1846 those buildings were connected. Fire once split this complex you see into three buildings kept eight feet apart, joined at last in 1846.