The Ford F-Series is a series of trucks marketed and manufactured by Ford since the 1948 model year. Slotted above the Ford Ranger in the Ford truck model range, the F-Series is marketed as a range of full-sized pickup trucks. Alongside the F-150 (introduced in 1975), the F-Series also includes the Super Duty series (introduced in 1999), which includes the heavier-duty F-250 through F-450 pickups, F-450/F-550 chassis cabs, and F-600/F-650/F-750 Class 6-8 commercial trucks. The most popular version of the model line is the F-150 pickup truck, currently in its 14th generation. From 1953 to 1985, the entry-level F-series pickup was the ½ ton F-100. The F-Series trucks have been developed into a wide range of design configurations during their production run. Alongside medium-duty trucks and "Big Job" conventional trucks (the forerunners of the Ford L-series), the model line has been sold as a chassis-cab truck and a panel van (a predecessor of the Ford E-Series). The F-Series has also served as the basis for multiple full-sized Ford SUVs, including the Ford Bronco, Ford Expedition/Lincoln Navigator, and Ford Excursion. The F-Series has been marketed by its three North American brands, as Mercury sold the model line as the Mercury M-Series in Canada from 1948 to 1968; Lincoln sold the F-Series during the 2000s as the Lincoln Blackwood and the later Lincoln Mark LT. Since 1977, the F-Series has remained the best-selling pickup truck line in the United States; it has been the highest-selling vehicle overall since 1981. The F-Series is the best-selling vehicle in Canada for over fifty years. As of the 2018 model year, the F-Series generated $41 billion in annual revenue for Ford. Currently, Ford manufactures the F-Series in four facilities in the United States.