The obvious success of the Liverpool & Manchester Railway demonstrated that steam railways were a safe, fast and efficient form of transport, and by the end of the 1830s ambitious entrepreneurs were planning a multiplicity of railways up, down and across the land. At first, the new railways were of purely local importance, but the need to connect important cities such as London, Birmingham, Manchester and Glasgow led to the promotion of major trunk routes, one of the first of these being the Lancaster & Carlisle Railway, which was authorised on 6 June 1844 as a northwards extension of the Lancaster & Preston Junction Railway. In its original form the Lancaster & Preston line was little more than a branch, but the establishment of railway communication between London and Scotland was regarded as a matter of national importance, and the L&PJ and L&CR lines thereby became vital parts of the West Coast Main Line. Building work was soon under way, and this important main line was opened as far as Kendal on 21 September 1846 and completed throughout to Carlisle on 15 December. The new railway, which ran through difficult terrain on its way to Carlisle, was a major feat of civil engineering, and its bridges, viaducts and other infrastructure stand to this day as tangible monuments of the early days of railway construction.