Maine and Vermont allow incarcerated felons to vote in prison by proxy in state elections. Other states have restrictions on voting by those convicted of felonies. There is no law preventing felons from voting in federal elections, reports ProCon.org.
The American Civil Liberties Union provides a state-by-state map where individuals convicted of felonies may check to find out if they are eligible to vote. Some states have a complete ban on voting by felons even after they have been released from prison, parole, probation and have paid outstanding fines. Some states allow felons to apply for re-enfranchisement, which restores their voting rights.