From 1963-1976 they were in their prime. Grand touring cars from the United States Road Racing Championship. Pony cars from the Trans-American Sedan Championship. Prototype racecars from the Canadian-American Challenge Cup. Open-wheel racecars from the Formula 5000 Championship. Touring cars from Trans Am. Then the Oil Crisis hit and things started to go downhill. Trans Am became more like IMSA GT, heavily modified even to the extent of including Winston Cup Cars. After a brief hiatus Can Am returned based on F5000 but to little avail, folding after only a few more seasons. The USRRC returned in 1998 after thirty years, including a Can Am prototype category, but was replaced after only a few seasons by the Rolex Sports Car Series.