Interstate 21

Interstate 21 (aka The Great Atlantic Coast Freeway) is a major north south Interstate Highway that runs along lots of Atlantic oceanfront from Massachusetts to Florida. It begins at the Mass Route 3/US 44 interchange in Plymouth, MA, and ends at Florida State Route A1A near Palm Beach, FL. I-21 runs slightly concurrent with I-95, except for it being mostly a coastal interstate. I-21 was first designated an interstate highway in 2023.