Missouri vs Tennessee

Missouri and Tennessee are closer than most pairs in this region, because both keep a child in a booster well past the common age-8 line. Missouri runs the booster to age 8 (with a release at 80 pounds or 4 feet 9 inches), and Tennessee runs it to age 9. The difference is what Tennessee adds around that booster. Tennessee requires rear-facing under age 1 and the back seat through the booster stage, neither of which Missouri sets. So while the two states are comparable on the booster itself, Tennessee is stricter overall because it protects the youngest children and locks in the back seat in a way Missouri does not.

Tennessee requires a child under 1, or 20 pounds or less, to ride rear-facing, and it requires the rear-facing, forward-facing, and booster stages to be used in the back seat where available. Missouri sets no rear-facing age and has no back-seat rule; it requires only that a child under 4 or under 40 pounds be in a child restraint. So a Tennessee parent can be cited for turning an infant forward or seating a young child up front, while a Missouri parent cannot. Both states recommend rear-facing and the back seat as best practice, but only Tennessee writes them into law.

This is where the two states almost match. Missouri keeps a child in a car seat or booster until age 8, with a release at 80 pounds or 4 feet 9 inches. Tennessee keeps a child in a booster until age 9, or until they reach 4 feet 9 inches, just one year longer. Both fines land at the same place: $50, with court costs added in Missouri and none added in Tennessee. So for a typical school-age child of average height, the booster experience is similar on either side of the line, separated by a single year. The American Academy of Pediatrics recommends a booster until the seat belt fits in both states, often past age 9.

The law that applies is the law of the state you are physically driving in. Missouri and Tennessee meet at the Missouri Bootheel, where I-55 and the I-155 bridge at Caruthersville connect the two near the Memphis approach. To stay legal across the whole trip, follow Tennessee's stricter rules: rear-face under 1, keep a child in a booster until age 9 or 4 feet 9 inches, and seat them in the back. A family moving from Missouri to Tennessee will find the booster stage familiar, just a year longer, but will pick up a rear-facing requirement and a back-seat rule that Missouri did not have.