Along with the Lincoln Highway and the National Old Trails Road, the PPOO was one of the earliest named transcontinental highways in the named highway era, roughly 1912 - 1926. The federal highway numbering began in 1926 but the names persisted for several years after that, at least into the 1930's and some for decades. There were hundreds of named highways from local routes to the cross-country roads, most of them supported by some sort of booster organization. The more important routes and the popular tourist routes had published maps and guides. Here are a few examples.


  • 1915 Rocky Mountain Highway
  • 1920 Intermational Parks Highway
  • 1920 Mohawk Trail
  • 1923 National Park-to-Park Highway
  • 1925 Corley Mountain Highway
  • 1925 Old Oregon Trail & Columbia River Highway
  • 1925 Skalkaho Highway
  • 1926 Pacific Highway
  • 1927 Shenandoah Valley Route
  • 1927 Storm King Highway
  • 1928 Lincoln Highway and William Penn Highway
  • 1928 National Highway (National Old Trails Road)
  • 1929 New York Central Route
  • 1930 Appalachain Scenic Highway
  • 1930 Cascade International Highway
  • 1930 King's Highway - Canada
  • 1930 Pacific Coast Highways
  • 1930 Peace River Highway - Canada
  • 1932 Old Spanish Trail
  • 1932 Shenandoah Valley Route