According to early records, the Warren Mill was the first building constructed east of the Oshawa Creek on the north side of King Street West.
The mill was constructed by John Bolase Warren in 1837 and acted as a flour and grist mill for the community. It was the largest operation of it type in the area. The mill was powered by water that came down the raceway over what is now MacMillian Drive. Warren ran the mill from the time of its construction until 1867 when he sold it to the Gibbs Brothers. The brothers operated the business from 1865 until 1883. The business then became known as the Oshawa Milling Company from 1884 until 1888. Ownership of the mill changed hands at least two more times between 1888 and 1892 when it came under the ownership of the Ontario Loan and Savings Company.
While under the ownership of the Ontario Loan and Savings Company, the mill was leased to Campbell and White who continued its operations. In 1922 the building was leased to the Argue and MacLaughlin Co. who operated a coal business.
The mill itself was a six storey wooden frame building that fell into disrepair. The decision was made to tear what remained of the building down in 1977. There is a plaque honouring the mill located on the parking garage that replaced it.