From this point all American road mileage was supposed to have been measured.

Zero Milestone

Washington, DC

Most people don't realize the significance of the Zero Milestone, and just use it as a base for their smartphones while taking selfies in front of the White House. It's an inscribed granite block, set inside a big brass compass on the sidewalk, about four feet high. It was not paid for by the federal government, but by the National Highway Marking Association, a lobbying group that wanted taxpayer money to pay for more road signs.

Zero Milestone and Washington Monument: important governmental neighbors.

The spot was chosen because it was, as inscribed in the monument's side, the "Starting point of the first transcontinental motor convoy over the Lincoln Highway. 7 July 1919." The convoy was the brainstorm of the U.S. Army, which wanted to find out how long it would take military vehicles to drive cross-country in case America was attacked. The answer was: a very long time.

The Army trucks, cars, motorcycles -- and even a large boat, the "Mayflower II," hauled on a five-ton trailer -- endured a road trip from hell. It turned out that the Lincoln Highway was, in many places, just a wretched track of mud. Vehicles slid into ditches, tumbled down mountainsides, and crashed through 88 horse-and-buggy-era bridges, including 14 on one day in Wyoming. Twenty-one of the convoy's 297 soldiers had to be sent home because of injuries. Nine of its 72 vehicles were destroyed en route and had to be abandoned (The boat only made it as far as Nebraska). The convoy tallied 230 accidents before it arrived in San Francisco two months after it began.

The Zero Milestone commemorated America's first transcontinental motor convoy: a road trip from hell.

June 4, 1923: President Harding dedicates the Zero Milestone.

The awful state of America's roads was a scandal. One of the junior officers on the trek, Dwight Eisenhower, later became U.S. President. It was partly his memory of the calamitous 1919 road trip that spurred his 1956 backing of America's new Interstate Highway System.

But the Zero Milestone isn't just a monument to the convoy. It mimics the "Golden Milestone" of ancient Rome, and was expected to be the spot from which all road distances in the U.S. would be measured. This was almost as bad an idea as driving cross-country with a boat in 1919. People in states such as Oregon and California hated the thought that their road distance markers would begin and end in the 3,000s. States began erecting their own Zero Milestones. With the threat of competing (and confusing) distances on the same highway mileposts, the idea was quietly dropped.

President Warren Harding dedicated the Zero Milestone on June 4, 1923. It was one of his last official acts in Washington before setting out on his own cross-country trip. He died in California less than two months later.

Like the convoy, he ended up in San Francisco, at the end of another bad trip from the Zero Milestone.