This paper documents and explains the recent rise of “big-box” general merchandisers. Data from the Census of Retail Trade for 1977–2007 show that general-merchandise chains grew much faster than specialist retail chains, and that general merchandisers that added the most stores also made the biggest increases to their product offerings. We explain these facts with a stylized model in which a retailer’s scale economies interact with consumer gains from one-stop shopping to generate a complementarity between a retailer’s scale and scope.