Wall Street's major indexes closed lower on the final trading day of 2025, concluding a year marked by significant gains despite tariff uncertainties and a strong surge in AI-focused stocks. The S&P 500, Dow, and Nasdaq all achieved double-digit percentage increases for the year, extending a multi-year bull run. This rally was largely driven by investor enthusiasm for artificial intelligence companies, pushing indexes to record highs. The Dow also recorded its longest monthly gain streak since 2017-2018.