Party City is a one-stop party supply shop that would take the hassle out of party planning. We are the worlds largest party supply retailer, with over 500 stores in the United States and Puerto Rico. The first year the store was opened, Party City had the idea to sell Halloween costumes and products. It was so wildly successful, that the following year, a warehouse space at the back of the building was used to house the costumes - and so the name Halloween Costume Warehouse, because it was literally Halloween costumes housed in the warehouse! This extra 2000 square feet dedicated to Halloween would prove to be one of the cornerstones of Party Citys success over 20 years later.