After the First World War, the wooden pier and storage areas were constantly under repair. In 1925, a breakwater consisting of 11,134 tons of broken stone was constructed. The following year, a wharf of concrete and steel was built.
In August 1930, just as the Great Depression was starting and after a decade of improvements, the official re-opening of the harbour took place.
According to the local newspapers, approximately 3,000 people attended the opening. Three steam ship lines raced to see whose ship would be the first to enter the harbour. The City of Kingston, owned by Canada Steamship Lines, made it, to the cheers of thousands. General Motors, Pedlar People and Fittings were first to ship out of the new harbour, loading the City of Kingston with cars and 30 tons of manufactured goods.
Throughout the 1930s, the harbour continued to expand: storage sheds were added over the years, steel harbour walls were extended, and roads were built to serve the area. The west pier was built at this time by William Bermingham and Sons of Kingston. The 1,082-foot (330 metres) structure was built 42 feet (12.8 metres) to the west of the old structure, widening the entrance to the port. In 1939, the outer harbour was dredged to a depth of 24 feet (7.3 metres) and the inner harbour and turning basin was dredged to a depth of 22 feet (6.7 metres).
The Midland Prince unloads coal at the Oshawa Harbour. Enjoy this video clip with an English Transcript.
In 1932, the eight-lock Welland Ship Canal introduced larger ships to Lake Ontario, that originally could not operate beyond Lake Erie. This increased business for the harbour in Oshawa. When the first ship arrived that year, a top hat was presented to the captain. The top hat is not only awarded at Port Oshawa, but is a maritime tradition at all ports.
In 1959, the St. Lawrence Seaway opened to excitement from the shipping community. Although, it was later learned that sections of the seaway were not large enough to handle ocean-going vessels.
The problems with the seaway did not concern city officials in Oshawa in 1960, they saw the waterfront as a perfect opportunity for drawing economic development into the area.
Michael Starr, MP for Ontario County, was instrumental in getting the Oshawa Port commissioned under an act of Parliament. The new Harbour Commissioners Act was proclaimed in 1962 with an autonomous body of commissioners – two federal appointees and one City appointee. The Oshawa Harbour Commission was now one of seven commissioned deep-sea ports in Canada.
The first meeting of the commissioners took place at the Genosha Hotel on December 12, 1960. Harbour staff at the time included a wharfinger, who managed the wharf, and a harbour master, who booked ships.