The big box retailer has updated its website with an August 2025 opening for the long-awaited Newmarket location under construction at 107 Harry Walker Pkwy. While the Newmarket location will indeed be the first within the municipality's borders, locals aren't exactly starved of the wholesale giant. Costco already operates a location at 18182 Yonge Street in East Gwillimbury, which is quite literally just a few steps north of Newmarket's northern boundary. So, while Newmarket's first Costco from an official standpoint, the new location opening this summer will not be locals' first taste of the brand's big box savings. But it won't necessarily be an expansion, as Costco plans to transform its existing location north of Newmarket into a business centre once the Harry Walker Parkway location opens.