During the last two decades, e-commerce has grown faster than any other retail subsector, but its effects have been varied for different retail industries. This work looks at the evolution of the retail sector in the U.S. over the 1987-2012 period, and relates it to the emergence of e-commerce. Chapter 1 documents the differences in labor productivity dynamics over the 1987-2012 period for three industries that have likely been affected by e-commerce competition, such as Clothing Stores, Shoe Stores, and Electronics Stores, and compares them to those of Grocery Stores, which have only recently seen the entry of online competitors. I find that productivity kept rising after 1997 for Grocery Stores, while stagnating for the other industries considered, which is consistent with e-commerce having an effect on the productivity dynamics of these industries. Selection effects seem to be present across all industries in all periods analyzed, while I find evidence of learning-by-doing only after 1997. Chapter 2 quantifies the role of e-commerce diffusion in the decline of department store sales, and analyzes the productivity responses by retail chains operating brick-and-mortar stores. I develop an empirical model of supply and demand for retail goods at the firm-MSA level. This model captures economies of scale in network size as well as adjustment in labor, while incorporating monopolistic competition and allowing for markups to vary in time. Since physical output is not observed, e-commerce provides me with demand shifters that are used to control for price variation. Using a novel dataset that combines confidential establishment-level data from the US Census of Retail Trade and private data on e-commerce diffusion from Forrester Research, I find a sizeable immediate effect of e-commerce on demand, and a small but significant productivity response to e-commerce diffusion. Estimating the production parameters separately from the markups, I find evidence of increasing returns in the size of the local network of stores. Finally, markups are increasing between 1992 and 1997 but decreasing after the introduction of e-commerce, which is consistent with a reduction in the market power of department store chains. In Chapter 3, I decompose the productivity estimates from the previous chapter into within- and between-firm dynamics, and relate each component to firm rationalization and e-commerce pressure at the market level. My findings show that productivity gains do not seem to come from market shares being reallocated towards more productive chains, suggesting that search costs are not a crucial factor in explaining productivity in the sector. I also find evidence of retail chains selecting which stores to operate locally based on establishment productivity, but the productivity gains are very small, which contributes to explain why we don't see large exit in the sector.