The M6 is the UK's longest motorway, running from the Catthorpe Interchange on the M1 near Rugby, to the A74(M) near Gretna Green on the border with Scotland, running for 232 miles (374km).
Part of the M6, the Preston Bypass, was the UK's first motorway to open to traffic in December 1958. Over the next decade, most of the rest of the motorway was constructed, and by May 1972, the M6 was complete between the M1 and Carlisle, leaving a few mile gap between Carlisle and the A74(M) at Gretna, which was finally constructed in 2008.
There were plans in the 1990s to renumber the A74(M) and M74 in Scotland as the M6, but this plan has been dropped.