The Mobilong Military Sheet is situated between longitudes 139°00and 139°30 and latitudes 35°15and 35°00, extending over the eastern most slopes of the Mount Lofty Ranges and the flanking plains of the Murray Basin. It is bounded by the following previously published sheets – Mannum (1957), Echunga (1954), and Alexandrina (1958). The most comprehensive work previously published and related to this sheet is that of Dickinson (1942). Access to the area is provided by a system of good all weather roads. It is traversed by the Princes Highway – the main road connection between Adelaide and Melbourne and by the broad (5 feet 3 inches) gauge railway linking the same capital cities. A subsidiary rail line extends from Monarto South northerly beyond Pallamana to Sedan. Murray Bridge is the principal township having a population of 5,500. Tailem Bend is important as a rail junction. Jervois, Monteith and Swanport are small settlements on the River Murray flats where intense irrigation of fertile pastures supports dairying pursuits, while at Mypolonga irrigation area cirtrus and stone fruits are produced. Kanmantoo and Callington are survivals of an era of copper mining in those districts. The average annual rainfall for the area is in the 12 to 15 inch range; figures for various recording stations being Mypolonga 12.11 inches, Murray Bridge 12.21 inches, Callington 13.94 inches and Tailem Bend 14.75 inches.