You may have wondered how “420” came to be code for marijuana consumption. It originated in 1971 with a group of high-school slackers in Marin County, California. (Side note: there’s a really good place to eat in San Rafael.) The term has become so pervasive that since Colorado legalized pot-for-fun in 2012, milepost 420 markers have been disappearing at an alarming rate from Interstate 70. As a remedy, the Department of Transportation has replaced the marker with milepost 419.99.
Although Idaho has not legalized marijuana, they’ve had the same problem on U.S. Highway 95, just south of Coeur d’Alene. Who knows why that’s happening in neo-Nazi country? Idaho can handle only one decimal place, though, so they marked the highway as milepost 419.9.