The Federal Election Commission maintains a list at FEC.gov all individuals who have filed Form 2 with the commission, officially declaring their intention to seek the presidency of the United States. As of Sept. 16, 2015, the FEC lists 1,107 individuals as having filed that form.
The New York Times and The Atlantic each also maintain updated lists of major candidates running for the nominations of the Republican and Democratic parties on their websites. There are 16 major candidates seeking the Republican Party nomination, following the withdrawal of former Texas Governor Rick Perry. In the race for the Democratic Party nomination, five candidates, including former First Lady of the United States Hillary Clinton, have filed the necessary paperwork.