The Manchester & Leeds Railway was sanctioned by Parliament in 1836 as a railway commencing at Manchester and terminating at Normanton, from where trains would reach Leeds via the North Midland Railway. Although Leeds is only 35 miles from Manchester, the hilly nature of the surrounding terrain meant that the company engineers adopted a circuitous route through Rochdale, Todmorden, Hebden Bridge and the sinuous and steep-sided Calder Valley. The 'Calder Valley' line was opened between Manchester and Littleborough on 3 July 1839, and further sections were brought into use on 5 October 1840 and 3 January 1841. The railway was completed throughout on 1 March 1841. The completed railway was heavily engineered, the Summit Tunnel between Littleborough and Walsden being the longest in the world at the time of its construction. This highly scenic line still forms part of an important rail link between Manchester and Leeds, although trains now travel on a shorter route via Halifax and Bradford. The eastern half of the route also forms part of separate Trans-Pennine route via Todmorden, Burnley and Blackburn.