To celebrate the 50th anniversary of Bikecentennial ’76, this two-part series tells the extraordinary story of four bicycle pioneers – Greg and June Siple, Dan and Lys Burden – who took a circuitous path from a shared dream to successfully staging a massive bicentennial event. Ultimately, more than 4,000 cyclists would ride their newly hand-mapped, 4,200-mile Transamerica Bicycle Trail. Before Bikecentennial, the four were active members of the Columbus, Ohio, chapter of the American Youth Hostels. It was during these early years that Greg Siple and his father founded the Tour of the Scioto River Valley (TOSRV), an event that eventually grew to attract thousands of riders and established the logistical blueprint for modern, multi-day supported bicycle rides. Eager to extend their horizons, the two couples embarked in 1972 on the audacious Hemistour, a historic expedition to cycle from Alaska to Argentina. The first leg of this monumental journey earned them a feature in the May 1973 issue of National Geographic. Titled “Bikepacking Across Alaska and Canada,” the article is widely recognized for introducing what may be the earliest use of the word “bikepacking” in print. Part 1 explores the origins of the group’s ambitions, the creation of TOSRV, and their grueling months riding together on Hemistour from Anchorage, Alaska, to Salina Cruz, Mexico. Part 2 will cover their lives after the group parted ways. While the Siples pressed onward to Ushuaia, Argentina – making June Siple the first woman to bicycle the entire length of the Americas – the Burdens returned to the United States to begin the monumental work of organizing the improbable Bikecentennial ’76.