U.S. Citizens do NOT need a passport to travel to St. Croix.
You're a U.S. Citizen in a U.S. Territory after all.
You do still have to clear U.S. Immigration and Customs because we are a Port of Entry but you'll do it in our quick and easy Pre-Clearance Facility before boarding your plane home.
AND if you have Global Entry, bring that card with you and you'll skip to an even shorter line at Customs.
No long Customs lines at International arrival airport.
By the way, TSA Pre-Chek works here too.