The railway was soon extended from both ends and northwards via a branch from Baker Street. It reached Hammersmith in 1864 and Richmond in 1877, and completed the "Inner Circle" in 1884, but the most important route became the line north into the Middlesex countryside, where it stimulated the development of new suburbs. Harrow was reached in 1880, and the line extended as far as in Buckinghamshire, more than from Baker Street. From the end of the 19th century, the railway shared tracks with the Great Central Railway route out of Marylebone station.