The Agency was created as a result of the opening of the Port Pirie to Crystal Brook line in December 1875. This was further developed in stages up to June 1887, when the Peterborough to Cockburn section was completed. Later stages were completed during the period 1910-1937. It was the smallest division from the view point of mileage, total being 384 miles, made up of 5ft 3ins (broad gauge), 4ft 8in (standard gauge) and 3ft 6in (narrow gauge).
 
Mr McArthur, was appointed Traffic Superintendent in 1887 and arrived in Peterborough to take charge of the Division. Between the years 1911 and 1914 the Port Pirie to Cockburn track was recognised as the busiest single track railway in the world.
 
During 1963 approval was announced for the Standardization of the Port Pirie to Cockburn line which also covered the conversion of the Terowie to Peterborough line. The project was undertaken as part of the work included in the 1949 standardization agreement between the Commonwealth and South Australia Governments. during 1968 agreement was reached with the Commonwealth, New South Wales and South Australian Governments to extend the sections between Cockburn and Broken Hill. This work was also included under the 1949 agreement. The total standardization project was completed in 1969 and opened for traffic on 16th January 1970. This conversion allowed a standard gauge train (the Indian-Pacific) to operate between Sydney and Perth via
Port Pirie.
 
Although CA 3970, South Australia Railways Commissioner, ceased in 1975, the Peterborough Division continued to be known as the above title until March 1978 when Australian National Railway took
over the running of non-urban railways in South Australia.
 
From 1875 to 1918 Peterborough was known as Petersburg
 

Historical agency address
Railway Terrace, Peterborough SA
Legislation administered
Creation: The Petersburg and Border Railway Act 1884 (No. 328)
Abolition: Commonwealth Acts No. 26 of 1975, Australian National Railways Act 1975

Superior agency unregistered

1975-1978: Subject to further research