From the website listed above:
"In 1953 Route 6 was designated the "Grand Army of the Republic [GAR] Highway" and signed as such in all fourteen states through which it ran. Through the sixties and seventies, the signs--along with the memory--of the GAR Highway gradually disappeared. Then, probably in the early 1990s, this name was revived and it appears on signs in all fourteen Route 6 states (numerically ranging from four in California, to nearly 100 signs in Indiana).
Dozens of Route 6 segments have interesting histories. The stretch from Los Angeles north to the Owens Valley was once known as "El Camino Sierra," and parts of it are still called "Sierra Highway." The stretch across the basin and range country from Tonopah to Ely, Nevada was part of the Midland Trail (also called the "Midland Roosevelt Trail"). Promoted by the Automobile Club of Southern California, in Los Angeles, the Midland trail connected that rapidly growing urban place (which grew past 1 million population in the early 1920s) to the Lincoln Highway. Perhaps this attempt to link with the Lincoln Highway, the most famous of the named highways of the time, was one effort by Los Angeles to connect to the rest of the nation in the rapidly emerging automobile era in which it was playing a central role. This route, however, had to take a back seat to Route 66, which became the prime link eastward from Los Angeles from the 1920s, through the Dust Bowl migration years, and until the 1950s. "...Kingman, Barstow, San Bernardino...."
Iowa presents another interesting case. Significant parts of the "River to River Road," which was built in a day across Iowa in 1910, became Route 6. Its construction consisted of a massive coordinated effort in which people in every township along the way improved and signed the road. In the 1920s, the path that Route 6 would later take was signified by utility poles that were painted white, creating the "White Pole Road," or "White Way Highway." All such designations had disappeared a long time ago-until the Spring of 1999 when a series of "White Pole Road" signs appeared along Route 6 in Cass County, Iowa. In Nebraska, signs still exist that indicate former name of the road, "Detroit-Lincoln-Denver" (DLD), or "Omaha-Lincoln-Denver" (OLD) highway."
The geocache should present no problem to find. The idea here is the story involved. Park safe. Be safe. Have fun!