The "Cloud Snapple Half Marathon" starts at Carderock Recreation Area, off the Clara Barton Parkway, outside the I-495 Capital Beltway. The course follows the historic Chesapeake & Ohio Canal Towpath under the Beltway, from near Milestone 11, past Lock 14 through Lock 5, on a mostly flat 100% gravel path. The turnaround point is just west of Chain Bridge, about 3/4 mile past Milestone 5. The course is USATF-certified with no road crossings and one short concrete dam at Milestone 5. Preserving America's colorful Canal era and transportation history, the Chesapeake & Ohio Canal National Historical Park is 184.5 miles of adventure. Originally, the C&O Canal was a lifeline for communities and businesses along the Potomac River as coal, lumber, grain and other agricultural products floated down the canal to market. Today millions of visitors hike or bike the C&O Canal each year to enjoy the natural, cultural and recreational opportunities available.