Hotels you can book at 18 in Alabama
An Alabama front desk can still demand you be 21 after your money has gone through. The fix is one of the state's 18+ hotels, and the right hotel starts with the right city. Spend your first minute below picking your city, and the rest on the room.
3 hotels
Birmingham
Hotel list coming soon
Huntsville
2 hotels
Mobile
4 hotels
Montgomery
Hotel list coming soon
Tuscaloosa
What each Alabama city is actually for
A carnival weekend and a statehouse errand do not land in the same part of Alabama. Mobile is the port city on the Gulf end, with a carnival season that builds to Mardi Gras. Montgomery is the capital, chosen in 1846, in central Alabama on the Alabama River, and a trip built around state government business belongs there. Both cities sit directly on I-65, which is worth knowing for the drive in once your trip has picked one of them.
Birmingham and Tuscaloosa hold the middle of the state for different reasons. Birmingham is the valley metro, set in Jones Valley in the state's Appalachian belt, and the concurrent I-20/59 corridor runs through the city. Tuscaloosa, on the Black Warrior River about 60 miles southwest of Birmingham, is the college town; the University of Alabama and its roughly 1,400-acre campus are there, so a campus visit is a Tuscaloosa trip, not a Birmingham one.
Huntsville is the North Alabama choice, near the Tennessee River, and the U.S. Space & Rocket Center is in Huntsville, so that one venue can settle the city question by itself. Huntsville is not on I-65; a 22-mile interstate spur, I-565, connects the city to the interstate. One of these identities usually matches the reason you are traveling, and that match is most of the decision, because comparing hotels for 18-year-olds only makes sense inside a single city.
Alabama's Gulf beaches are a separate leg of the trip
The Gulf-front sand is about 50 miles from Mobile, roughly an hour southeast by road, on a stretch of coast that is its own place rather than part of any city above. Mobile itself has a different relationship with the water. Founded by the French in 1702, it is Alabama's oldest city and a major port for the region, near the Gulf's deep water, and its carnival season peaks at Mardi Gras.
Plan around that hour rather than against it. A Mobile base can still carry a beach day, but a trip that is mostly towels and salt water puts an hour of road between the room and the shore, each way, every time. Book Mobile when Mobile is the point, and let the beach be the day trip instead of the reason you picked the room.