Field was created solely to accommodate the Canadian Pacific Railway's need for additional locomotives to be added to trains about to tackle both Field Hill, and the Big Hill.
Following completion of the Spiral Tunnels which eliminated the Big Hill, Field remained an important place as it was still necessary to add helper (bank) engines to get trains over the steep 2.2% (116 feet to the mile, or 22 metres to the kilometre) grade of Field Hill.
Even bigger locomotives were needed and this time six massive 0-6-6-0 Mallet type (see: Whyte notation) were built (one in 1909 and five in 1911).
The Ottertail revision of 1902 and the five-mile (26,518 feet or 8.083 kilometres) long double track Connaught Tunnel of 1916 were other improvements made to the original line in British Columbia.
It was not until the late 20th century when a major new project of 20 miles (32 km) including the 9.1-mile (14.6 km) Mount Macdonald Tunnel reduced the grade to a very manageable average of 0.82%, (maximum 1%) opened in December 1988.