Just off a quiet stretch of US Highway 34, just 3 miles east of Trenton, Nebraska, stands a 35-foot tall shaft of Minnesota pink granite.  Near the top of the 91-ton monument is a carving of a Sioux warrior named John Grass facing west, and a Pawnee brave named Ruling His Son stares east.  The quiet prairie that surrounds the monument gives little hint at the events of August 5, 1873—the last battle between Great Plains Indians in North America that gave this location its name—Massacre Canyon.