Circle Launches USDC Stablecoin on Polkadot Asset Hub Circle, the issuer of the USD Coin (USDC), the second-largest stablecoin by market capitalisation, is expanding its reach by launching USDC on the Polkadot blockchain. On September 19, Circle officially introduced USDC Coin on the Polkadot network, making Polkadot USDC available to developers and users.