Mill City Museum (Washburn A Mill Ruins)

The Washburn A Mill was built in 1874 by Cadwallader C. Washburn on the west bank of the Mississippi River at St. Anthony Falls, the only natural waterfall on the Mississippi and the power source that made Minneapolis a milling capital. At its opening the mill was the largest flour mill in the world, capable of producing enough flour for 12 million loaves of bread per day.

On the evening of May 2, 1878, two dry millstones rubbed against one another, throwing a spark into the flour-laden air. The resulting dust explosion leveled the Washburn A and ignited fires that consumed several adjacent mills along the riverfront. Fourteen workers inside the A Mill died instantly; four more workers in neighboring mills died in the spreading fire, bringing the disaster's toll to 18. Mill manager John A. Christian identified flour dust as the cause, and two University of Minnesota professors later confirmed the diagnosis through controlled combustion experiments — work that reshaped milling safety worldwide.

Cadwallader Washburn rebuilt the mill on the same limestone foundation, with engineer William de la Barre designing dust collectors and improved ventilation. The rebuilt Washburn A operated from 1880 until 1965, by which time Minneapolis milling had migrated to Buffalo, NY and elsewhere. The empty hulk sat on the riverfront for decades.

On February 22, 1991, arson destroyed the rebuilt mill, leaving only the limestone exterior walls standing. Rather than demolish the ruins, the Minnesota Historical Society stabilized them and built a new museum structure inside the shell. The Mill City Museum opened in 2003 and has anchored the revitalization of the Minneapolis riverfront, including the adjacent Mill Ruins Park.