In 1861 Congress appropriated an additional $100,000 in order that John Mullan might reroute a portion of the Mullan Road in northern Idaho. The original route swung south of Lake Coeur d'Alene, but flooding hazards on the St. Joe River threatened the potential use of this section. The new portion of the road, north of Lake Coeur d'Alene, was heavily timbered and, as a result, Mullan and his crew found themselves in what is now known as Fourth-of-July Canyon on Independence Day, when they were scheduled to be at the Coeur d'Alene Mission, the intersection point with the older road.
It was on this day that the Mullan Tree, a white pine, received its inscription "M. R. July 4, 1861." The M. R. stands for Military Road, initials with which Secretary of War Davis had instructed Mullan to mark the trail at frequent intervals. Mullan apparently did not think this an unusual occurrence, because his "Report on the Construction of a Military Road from Walla Walla to Fort Benton "does not include any specific reference to this tree or to this day. However, the Fourth-of-July Canyon received its name from the day of celebration.
Others have made much of the activities of July 4, 1861, notably Addison Howard in his article on Captain Mullan:
The fourth of July found the crew in a thick cedar forest at the head of a canyon. Lieutenant Mullan suspended work and the road builders celebrated Independence Day in an old-fashioned patriotic manner. They exploded so much powder and punctured the scenery so freely with their rifles that lurking Indians, who had been molesting the crew, thought the whites had gone insane and discreetly withdrew into the forest. From then on they considered the road builders "bad medicine" and caused no further trouble. (Washington Historical Quarterly, July 1934, p. 193.)
In 1919 citizens of Idaho moved to have the tree designated as a national memorial. At that time the tree evidenced signs of decay. In 1931 faculty members of the University of Idaho's Forestry School examined the tree and discovered dry rot. In 1962, during a heavy wind storm, the top portion of the tree was blown off, leaving a 15 foot stump.
Today the tree stands a few hundred yards from Interstate 90 (Old U. S. 10), between Coeur d'Alene and Kellogg. There is a marked access road and a protective barrier around the tree, and the initials still appear on the stump.