More than half the US states require a voter to provide a specified identification document (ID) to cast a ballot at the polling place, and a few extend the requirement to absentee or mail-in voting. Many states require an ID with a photograph of the voter (photo ID). Some require a document that does not need to include such a photograph (nonphoto ID). Others do not require any type of ID to vote, but a voter may be asked to provide certain information to verify what is contained in the registration record or otherwise confirm his or her identity, such as stating an address or birth date or providing a signature. Voter identification requirements across the states vary in flexibility, in the types of documents allowed, in exceptions made to the requirements, and in the recourse available to a voter who cannot comply with the ID requirement at the polls. Photo ID requirements in particular have been a major issue of policy debate in recent years, but for both photo and nonphoto ID, the range of IDs accepted and how strictly the state enforces the requirement have also been sources of controversy. Debates over such requirements are typically complex and can be contentious. This book provides an updated overview of state requirements for voters to present some form of ID before casting a ballot in a federal election. The book also discusses the origins of voter ID, relevant federal legislative action in the 114th Congress, and selected legal and policy issues related to state voter ID laws.