A 1916 photo shows a District boundary stone located at South Capitol Street and Southern Avenue. Since 2013, cyclists have organized an annual bike ride to each stone, a 60-mile ad­ven­ture. (The District of Columbia Daught/The District of Columbia Daught)

Since 2013, a group of "history buffs, bike nerds, and adventure junkies" have convened each year for a bike ride around Washington's oldest monuments: boundary stones marking the edges of the 100-square-mile area that made up the original site for the nation's capital.

This year's 60-mile ride, held Oct. 14, began at the first stone, placed on April 15, 1791, at the south corner of Jones Point, and continued with visits to the 39 boundary stones that were subsequently laid at one-mile intervals between 1791 and 1792.

The stones are generally inconspicuous, even with the protective iron fences that surround most. But for some people, like Vaughn Edelson, who has organized the annual ride since it began, intrigue with the stones only grows. Edelson and a friend walked the original border, one side at a time, over the course of a year. In 2011, they caught the attention of the History Channel and were asked to appear in an episode of "How the States Got Their Shapes." She realized how many people had never heard of the boundary stones, which are common in cities.

The markers were "how you surveyed the property in those days," says Jane F. Levey, chief historian of the Historical Society of Washington, D.C. Boundary stones can still be seen in places such as Boston, along the New York-New Jersey border, and at the Mason-Dixon Line.

Cyclist M. Margaret Pratt of Arlington had periodically ridden past the District stones, but upon learning of their historical significance set a goal to visit each one. Pratt participated in this year's bike ride and saw every stone. "I never thought I'd do it all in one day," says Pratt, who spent nine hours on the tour.

Anyone with access to a reliable bike can re-create the boundary stones ride on their own by visiting Facebook and searching for "5th Annual Boundary Stone Bike Ride" to get a copy of the map from the official event page, Vaughn suggests. Whether you tackle one side at a time or go for all four, you can follow the event's lead.

After your ride, make your way to Boundary Stone (116 Rhode Island Ave. NW), a bar in Washington's Bloomingdale neighborhood. It hosts the official after-party each year.