In 1914, he began to practice as a public accountants He was the director of the National Bank of Australia after it merged with the Queensland National Bank. He was elected an alderman of the Windsor Town Council in 1912, becoming the Mayor between 1918 and 1923.
In 1937 and 1940, he stood and was elected the UAP member for the Federal Division of Lilley.
William Jolly retired from politics following his defeat in the 1943 general election. During his time as Lord Mayor, Jolly was responsible for many civic developments, especially the arterial road network in Brisbane.
The Grey Street Bridge (renamed the William Jolly Bridge shortly after his death) was built during his time in office. On 6 April 2013, William Jolly"s grandson Warren Jolly was a guest speaker at the reopening of the newly refurbished Brisbane City Hall, which was first opened by William Jolly on 8 April 1930.
Jolly was described as a family man who was active in church activities.
He attended Ashgrove State School. He began working as law clerk with at a small law firm and then moved to the larger Atthow & MacGregor while studying accountancy. William Jolly Bridge, crossing the Brisbane River between South Brisbane and the Brisbane Centre for Biodiversity Dynamics
Jollys Lookout, a locality in the Moreton Bay Region, named after his visit in 1927
West.A. Jolly Park, 50 Wesley Street, Lutwyche, Brisbane.