Under the Imperial policy of the time, namely the Royal Proclamation of 1763, which was rooted in Roman Law, Dorchester arranged to purchase more than of land from the Mississaugas in 1787. After surveying the land, the Mississaugas objected to the purchase and it was declared invalid. Another agreement would be made in 1805, but this agreement too fell into dispute and was only eventually settled two centuries later in 2010 for . A townsite was surveyed in 1788 by Captain Gother Mann, and laid out in a gridiron, with government and military buildings around a central square. The purchase did not include the Rouge River valley, yet to be settled.