In the early days of motorcars, promoters gave names to auto routes to boost tourist travel. Several named highways crossed significant portions of Wyoming, with Yellowstone Park a prime attraction. But by the mid-1920s the system had become chaotic. The government began numbering routes instead—gaining efficiency and sacrificing romance.
As mass production of automobiles increased the demand for better roads, federal highway funds became available to states and “good roads” committees pioneered the identification, improvement and naming of likely tourist routes. Among the first of these, from the Black Hills to Yellowstone, was the Black and Yellow Trail.