The Caledonian Railway was the largest of the three Scottish companies to go into the London Midland & Scottish Railway at the grouping in 1923. It contributed 1,077 locomotives, 3,040 coaches and over 50,000 goods vehicles running on more than 1,000 route miles of track stretching from the border city of Carlisle up to the Highlands and across to the East Coast. This book looks at how the 'Caley' system fared in the ownership of the LMS in which it became the dominant partner of the latter's Northern Division: the working of its main and secondary lines, infrastructure improvements, motive power, rolling stock and shipping developments, the challenge of the wartime years and the legacy left to British Railways at nationalisation.