Oshawa’s Polish community grew throughout the early years of the 20th century. In August 1922, 19 Polish residents met at the home of Stanisław Leśniak to discuss establishing a Polish organization in the community; this came to realization in September of that year when the Polish Society of Fraternal Help was established. The first president was Józef Mazurkiewicz. The group changed their name to the Polish Society in Oshawa in 1924.
In 1925, the organization decided to build a Polish hall, and construction began shortly afterwards at 219 Olive Avenue. All members donated $10 towards construction, and an interest-free loan from members was also approved. Fundraising initiatives looked outside the Polish community as well with a door to door collection. The hall was completed in 1928.
A number of community groups began operating out of the hall, including a library, choir, Polish language school, and amateur theatre group. As well, a Polish Veterans group started their base operations from the hall. During the war years, the group supported Poland and organized fundraising towards a relief fund. Members of the United Polish Relief fund visited each Polish family in Oshawa, held dances, and organized banquets, raising over $1800 towards the cause.
In April of 1944, the Polish Society of Oshawa decided to join the National Polish Alliance of Canada; they merged with another Branch in Oshawa, Branch 16, and together became Branch 21 of the National Polish Alliance of Canada. Wincenty Kołodziej was the first president of Branch 21.
Branch 21 has actively participated in Oshawa’s annual Fiesta Week for decades with dancing and traditional food being served. They operate as the “Poznań Pavilion.”