The Parks Board received approval to purchase 10.5 acres of land, originally known as Donohue Park, from Jeremiah J. Donohue for $28,000 on September 16, 1929. It was renamed Montgomery Park in 1945, in honour of Field-Marshal Viscount Montgomery of Alamein (1887 - 1976). When World War I broke out in 1914, Bernard Montgomery was one of the first to be sent to France. He was shot through the lung and at first thought to be dead. He recovered, however, to find himself a captain and the owner of a D.S.O. for bravery. He commanded one of the most decisive victories of World War II, the battle of El Alamein in Egypt. He also served as the deputy chief commander of N.A.T.O. from 1951 until 1958. This park was one of three parks renamed in 1945 to honour leaders of the British Empire during the Second World War. Churchill Fields Park (previously known as Westdale Park or Westdale Athletic Field) was named in honour of Sir Winston Churchill (1874-1965), the Prime Minister of England from 1940 to 1945. Mahony Park was renamed Crerar Park after General Henry Duncan Graham Crerar (1888-1965), a celebrated officer from World War II (born in Hamilton). However, almost 40 years later, local residents asked that the name Crerar Park be changed back to Mahony Park. This was approved on April 12, 1983.
The land was graded and plowed in 1945, and was developed in 1947. In 1955, a clubhouse was built which included dressing rooms for ball players and washrooms for spectators. By 1965, three acres of land facing onto Main Street had been established as a horticultural park. The rest of the land was used for sporting activities.
New playground equipment was installed in 1987. Multi-phase redevelopment of the park, according to plans approved by the neighbourhood, started in 1992. Among the improvements was a handicapped accessible creative play structure. On April 25th and 26th of 1992, residents raised funds for the construction of the playground by holding a garage, craft, and bake sale. For every dollar that was made at the event, the City donated $2 (to a maximum of $5,500). This project was completed in 1993.