On April 20, 1914, the National Guard set fire to the UMWA strikers' tent colony in Ludlow, Colorado, where miners had been living since the Colorado Fuel and Iron Company, owned by John D. Rockefeller, had evicted them from their homes.
Courtesy Fred and Frank Hefferly Collection, Box 8-E2, Archives, University of Colorado at Boulder Libraries.

Twenty-six people, including eleven children and two mothers (one pregnant) died in what became known as the Ludlow Massacre.
Courtesy Denver Public Library, Western History Department, X-60451.