The period during which the site or structure was constructed, installed or created. The classifications used for the SCRCA Project are:
- 0: Unknown = The date / period of construction, installation or creation has not yet been ascertained
- 1: Pre-69 = Prior to construction work commencing on the Settle-Carlisle line (prior to 1869).
- 2: MR-C = Midland Railway construction phase (1869 to 31st December 1876)
- 3: MR-O = Midland Railway operational phase (1st January 1877 to 31st December 1922)
- 4: LMSR = London Midland Scottish Railway operational phase (1st January 1923 to 31st December 1947)
- 5: BR = British Railways / British Rail operational phase (1st January 1948 to 31st March 1993)
- 6: Post-BR = After British Rail (includes Railtrack and Network Rail operational phases (1st April 1994 to present)