The line was built in parts between the 1830s and the 1860s with the first parts being the Grand Junction Railway (Warrington - Birmingham) and then the London and Birmingham Railway, both completed in the 1830s.
Despite its somewhat confusing singular name, the WCML is not a single railway line, but a series of interconnecting railway lines.
For instance there are two rail routes between Birmingham and Manchester, one which goes via Crewe, and one via Stoke-on-Trent, but both are part of the West Coast Mainline.
The line was modernised and electrified in the 1960s. It is currently undergoing a major upgrade along almost its entire length. The original plans estimated that this upgrade would cost £2bn, be ready by 2005, cut journey times to Birmingham to one hour (currently 1hr 40mins) and 1hr 45mins to Manchester. After a series of setbacks, in particular the bankruptcy of Railtrack, the revised estimates indicate that the cost will £10bn, be ready by 2008, Birmingham journey times will be 1hr 10mins and 2hrs to Manchester.