SAN JUAN, Puerto Rico (CNN) -- With surveys showing the outcome
                  too close to call, Puerto Ricans will vote Sunday on their future status within
                  the United States.

                  While the referendum is non-binding, a substantial vote in favor of making
                  Puerto Rico the 51st state would be used to push the U.S. Congress to
                  consider the idea seriously.

                  "I trust that when this process ends, we will have eradicated from our daily
                  lives a hundred-year debate that has overwhelmed and limited us," said Gov.
                  Pedro Rossello, a statehood advocate who put the measure on the ballot.

                  Puerto Rican voters will have five choices, which include becoming a state,
                  remaining a U.S. commonwealth, declaring independence or entering into a
                  "free association" with the United States that would be somewhere between
                  commonwealth and independence. The fifth choice on the ballot is "ninguna
                  de las anteriores," or none of the above.

                  Supporters of retaining commonwealth status are pushing for a
                  none-of-the-above vote because they object to the way the commonwealth
                  option is described on the ballot.

                  Polls show vote will be close

                  A poll released Wednesday by the San Juan Star newspaper found that 49
                  percent supported statehood, 45 percent said they would vote for none of
                  the above, 2.4 percent supported independence, 3 percent backed free
                  association and just 0.6 percent supported the commonwealth option as
                  written on the ballot.

                  A poll released Friday by El Nuevo Dia newspaper found that 48 percent
                  were planning to vote for none of the above, while 45 percent favored
                  statehood and the remaining 7 percent were split among the other options.
                  The gap between statehood and none of the above was within the poll's
                  margin of error.

                  Puerto Rico, which has 3.8 million residents, became a U.S. territory in
                  1898 as a result of the Spanish-American War. It became a commonwealth
                  in 1952.

                  Puerto Ricans are U.S. citizens subject to many federal laws and the military
                  draft. While they receive some federal benefits, they don't pay U.S. taxes
                  unless they move to the mainland.

                  Puerto Rico does not get voting representation in Congress, and residents
                  don't get to participate in U.S. presidential elections unless they become
                  residents of other states.

                  Statehood opponents fear cultural assimilation

                  Supporters of statehood say it would bolster Puerto Rico's economic
                  development and give its people full democratic rights enjoyed by other U.S.
                  citizens. But opponents fear that the mostly Spanish-speaking island's
                  language and unique culture will be lost if incorporated into the
                  English-oriented mainland.

                  "I implore people to come out and vote to break the agenda of assimilation
                  and imposition of statehood that they want to impose on these people," said
                  Anibal Acevedo Villa, leader of the Popular Democratic Party, which
                  supports commonwealth.

                  Under the current arrangement, the net amount of federal money transferred
                  to Puerto Rico each year is about $10 billion. Some in Congress who
                  believe that level of financial transfer should not continue have been trying to
                  push the island toward statehood.

                  "There can be no more free ride for Puerto Rico," said Rep. Dan Burton,
                  R-Indiana, in an interview with Caribbean Business weekly.

                  Mainland critics: 'Too foreign' for statehood

                  But opponents on the mainland say Puerto Rico is too poor, too remote and
                  too unlike the other 50 states to be considered for statehood.

                  In a commentary in the San Juan Star, Gerda Bikales of the group English
                  Language Advocates said making Puerto Rico a state would be "a nightmare
                  of our own making."

                  "I can assure the people of the island that mainstream America will not
                  accept into its fold a new political entity with all the characteristics of a
                  foreign nation," she said.

                  Carlos Vivoni, Rossello's economic development secretary, pointed out that
                  similar arguments were used against other U.S. territories that became
                  states. New Mexico had a majority Hispanic population when it was granted
                  statehood in 1912, and Florida was accepted in 1845 despite concerns
                  about widespread poverty and a small population, he said.

                  "We would expect a significant increase in the level of investment and in the
                  level of economic activity from a change in status towards statehood," Vivoni
                  said.

                  It has been nearly 40 years since Congress last created a new state, Hawaii,
                  in 1959.

                                 Reuters contributed to this report.