To become citizens of the United States, immigrants most often must be permanent residents for a period of time (usually 5 years). Permanent residents must pay taxes on their worldwide income and, in most cases, cannot vote. However, throughout the 19th century, many states did allow immigrants to vote after they had declared their intention to become citizens. This was primarily because these new states were populated in large part by immigrants who had not yet attained citizenship. Throughout U.S. history, non-citizens have been allowed to vote in 40 U.S. states and territories. As of 2005, non-citizens are allowed to vote in seven jurisdictions in the United States: Chicago and six towns in Montgomery County, Maryland.