The explosive growth of artificial intelligence has triggered an unprecedented wave of data center investment, yet systematic evidence on how these facilities affect local economies remains scarce. Guided by a framework linking the effect of digital infrastructure to local complementary factors, we study the local economic effects of data center entry in the United States using comprehensive facility-level data merged with county-level outcomes. Using the Callaway-Sant’Anna difference-in-differences estimator, we find that data center activation increases local business establishments by 1% over the first three years and 4.7% over the full period we observe. Employment and total wages also rise, alongside increases in building permits and median household income. These business and labor gains persist under narrower comparisons with neighboring untreated counties and synthetic difference-in-differences estimation. A sector-level decomposition shows that full-period establ ishment growth is strongest in information, construction, and real estate. The overall economic response also varies with host conditions and facility development. Specifically, local economic effects are larger in metropolitan than in non-metropolitan counties, total wage gains are larger for Big Tech than for other facilities, and counties receiving additional data centers within five years of first entry experience larger gains than those with isolated entries. On the cost side, the total electricity price rises by roughly 5% over the full observed period in counties whose utilities serve few other counties. These findings extend evidence on the returns to using digital infrastructure to the communities hosting its production, informing debates about data center expansion and local policy.