Polymarket US open interest reached $111.4 million by Aug. 22, nearly doubling since the 2026 FIFA World Cup concluded on July 19. A report cited in the update rounded the figure to $111 million and said it had nearly doubled from mid-July. The platform now represents 54% of total Polymarket volume, despite launching only in December 2025. Its growth contrasts with an approximately 20% decline in open interest across major prediction markets, including Kalshi, after the tournament. Polymarket US offers markets spanning politics, economics, pop culture and sports, while interest in the upcoming U.S. midterm elections may support further activity. The platform has also used KYC and geofencing measures to comply with U.S. restrictions. Existing information describes it as a fiat, dollar-denominated venue without crypto collateral or anonymous wallets, while the new account characterizes it as benefiting from stablecoin and broader crypto-ecosystem integration. The divergence may also reflect a shift from short-dated World Cup contracts to longer-term positions, allowing open interest to rise even as event-driven trading cools.