Nineteen states and Washington, D.C., have voter registration available on Election Day. Many also offer same-day registration and voting during the early voting period (see NCSL’s webpage on Same-Day Registration for additional information):
California, Colorado, Connecticut, District of Columbia, Hawaii, Idaho, Illinois, Iowa, Maine, Maryland, Michigan, Minnesota, Nevada, New Hampshire, Utah, Vermont, Virginia, Washington, Wisconsin, Wyoming and Puerto Rico
Montana and North Carolina offer same-day voter registration during the early voting period, but not on Election Day.