The St. Thomas Mount Cantonment lies about 8 miles South West of Madras and 3 miles South West of Saidapet. Pallavaram is about 11 miles South West of Madras and 6 miles South West of Saidapet. The length of the Cantonment from East to West 5 1/4th miles and North to South is 1 ¼th miles to 2 1/8th miles . At the instance of Lt. Col. James, Commanding the Artilery at Fort St. George to complaint of earlier inconveniences caused to his men by numerious public houses at Black Town now called George Town and of want of proper conveniences for practice at Vellore the Board of Directors agreed on 1st Dec 1774 to order the artillery from Madras and vellore to rendezvous at the Mount till further order. In 1805, the collector of Chengleput Distt. Surveryed the place, land marked of its limits with bound stones at the suggestion of the commanding Officer of the Cantonment in 1811 the limits of the Cantonment were extended 4 miles around it in order to restrict the immoderate use of spirituous liquors by the European troops at the Mount. In 1814 the limits of the Cantonment were again extended, so as to include the ground on which the Horse Artillery then always manoeuvred and the whole of a small hill on which it was desirable to place a solitary prison. In 1826 there was a further extension of the Cantonent in order to enlarge the artillery practice ground as the existing ground was only suitable for a mortar range and or preaching battery, whereas it was necessary to provide for two 'enfilading batteries'.
In 1830, the Military Authorities asked the Government to Marked by boundary stones the limits of the Cantonment and to, at the same time, include within the said limits a small village on the South West side of the Cantonment merely for purposes of Polica and another plot of ground on the North West for military purposes, viz. for extension of the bullock lines. How this request was disposed of is not known, as the records bearing on the point from 1831 to 1842 are not traceable. In G.O. No.139 dated 1st June 1832 the Cantonment was constituted a Military Bazaar Station the administration of Regulation VII of 1832 being vested in the Station Staff Officer under the orders of the Officer Commanding. In 1846, the limits of the Cantonment as it then existed; weer marked by boundary stones. In 1852, the Hob'ble Parcheri which was inhabited by camp followers and residents of the Cantonment was included within its limits. In 1856 a description of the boundaries of the cantonment was furnished by the Military Department to the Government for approval and the Govt. approved the description. In 1860, the limits of the cantonment were extended, and in the same year a notication was published in the Fort St.George gazette declaring St. Thomas Mount to be a Military Cantonment within the meaning of Madras Act no.IV of 1865 . In 1869 some land was selected as a site for the Snider Ammunition Factory and included within Ammunition Factory and included within the cantonment limits. In 1876 there was a further extension of the limits of the cantonment in order that the conservancy of a dense paracheri close to the houses of some Europeans, Staff Sergeants etc. might be brought under direct control and supervision. In 1878, the site of certain objectionable huts at St. Thomas Mount was acquired, as it was doubtful whether the Commanding Officer had power for sanitary reasons to eject the tenants and level the huts.
In 1890 there was a further extension of the limits of the cantonment, but the area newly included was not acquired or purchased by Government from the proprietors. From 1st April 1890 certain taxes were imposed in the cantonment under Section 21, Act III of 1880. In 1899, the boundaries of the cantonment were revised by adding some land to it and excluding a small portion of land from it. The revised boundaries of the cantonment as also of the Mount Bazaar and Bengali Bazaar were notified in the Gazette of that year. In 1905, the Government of India sanctioned the amalgamation of the Pallavaram Cantonment with this cantonment , as the Native Infantry Depot at the latter place had been withdrawn, and as the Commandant of the Depot ceased to be Special Magistrate at Pallavaram, when the Depot was withdrawn. But, for want of the final orders of Government on the exclusion of the Saidapet Water Works from the St. Thomas Mount cantonment, the notification or the combined cantonments was not published in the gazette till 1911. In 1914 and again on 7th January 1919, revised descriptions of the boundaries of the combines cantonments were published in the Fort St. George Gazette. On 7th July 1927 a notification was published in the Gazette excluding the Sadar Bazaar - better known as the "Bengali Bazaar" from the cantonment of St. Thomas Mount cum Pallavaram.