A southern extension from Port Robinson opened in 1833, with the founding of Port Colborne. This extension followed the Welland River south to Welland (known then as the settlement of Aqueduct, for the wooden aqueduct that carried the canal over the Welland River at that point), and then split to run south to Port Colborne on Lake Erie. A feeder canal ran southwest from Welland to another point on Lake Erie, just west of Rock Point Provincial Park in Port Maitland. With the opening of the extension, the canal stretched between the two lakes, with 40 wooden locks. The minimum lock size was , with a minimum canal depth of .