Welland Canal 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 . Deterioration of the wood used in the 40 locks and the increasing size of ships led to demand for the Second Welland Canal, which used cut stone locks, within just a few years. In 1839 the government of Upper Canada approved the purchase of shares in the private canal company in response to the company's continuing financial problems in the face of the continental financial panic of 1837.
Welland Canal affiliated with the canal, and was actually used to help transfer cargoes from the lake ships, which were too large for the small canal locks, to the other end of the canal (The Trillium Railway owns the railway's remnants and Port Colborne Harbour Railway). Smaller ships called "canallers" also took a part of these loads. Due to this problem, it was soon apparent the canal would have to be enlarged again. In 1887, a new shorter alignment was completed between St. Catharines and Port Dalhousie. One of the most interesting features of this third Welland Canal was the Merritton Tunnel,