De Mores Packing Plant Ruins, Historic meat processing plant ruins in Billings County, United States.

The De Mores Packing Plant Ruins occupy a 20-acre site along the east bank of the Little Missouri River near Medora, now kept as Chimney Park. Only the slaughterhouse chimney and one other structure survive; markers placed at the foundation corners under a Works Progress Administration project outline the slaughter house, power house, cooper shop, fertilizer room, three ice houses, cooling and storage building, loading platform and holding pens.

The Marquis de Morès, a French nobleman and pretender to the French throne, arrived at Little Missouri in April 1883 and built the packing plant that same year. It could process 150 cows per day, but the venture failed and closed in 1886. The building burned on March 17, 1907; the state acquired the site in 1936 and listed it on the NRHP in 1975.

The ruins show how meat processing shaped life in this region and the role that modern factory work played in developing the American frontier. Visitors can sense at the remaining foundations how intensely this place was once used.

The site can be reached through a public park in town and features informational signs at the foundation corners to help visitors understand the layout. Walking around is easy since the ruins sit on level ground.

The Marquis de Morès, a pretender to the French throne, built the plant to slaughter and process cattle beside the range, cutting out the cost of feeding live animals on the trip east and eliminating "the middleman" by shipping beef straight to consumers. The slaughterhouse chimney is the most conspicuous landmark left.