It's not a final step, but Puerto Rican governor Ricardo Rossello says a referendum Sunday sends a clear message to U.S. Congress and the world: the island commonwealth wants to become the 51st state. Puerto Rico has been a U.S. territory since 1898.

Governor Rossello, who was inaugurated in January, had promised today's referendum as a platform during his campaign. Of Puerto Rico's 2.26 million registered voters, nearly 23 percent cast ballots, with a reported roughly half-a-million votes in favor of statehood, only about 7,600 preferring independent status, and approximately 6,700 wanting to maintain status quo.

The referendum is non-binding, and could be subject to challenge. Many are questioning the validity of the vote amid a low turnout and a boycott by several opposition parties. Regardless of the final outcome, U.S. Congress has final say regarding Puerto Rico's political status.