Colorado vs Wyoming

Colorado and Wyoming are more alike than most neighboring pairs at the older ages, which makes the one difference between them stand out. Both keep a child in a car seat or booster until age 9, and both require children to ride in the back seat through age 8. Where they split is at the very start. Colorado, under a law effective January 1, 2025, requires a child under 2 to ride rear-facing. Wyoming sets no rear-facing age at all. That single rule is why Colorado is the stricter state: the two laws are nearly identical for a school-age child, but Colorado adds a legal rear-facing requirement that Wyoming leaves to the parent.

Both states use age 9 as the booster line with no 4 feet 9 inch shortcut, so a child stays in a car seat or booster until their 9th birthday in either. Both also require a child under 9 to ride in a seat other than the front seat where one is available. For a 5, 6, 7, or 8 year old, the two laws are effectively the same: booster, in the back, until age 9. A family with school-age children will not notice any change crossing the line, which is unusual for two neighboring states and reflects how close their later-stage rules are.

Colorado requires a child under 2 who weighs less than 40 pounds to ride rear-facing, and a child 2 to 3 under 20 pounds to remain rear-facing as well. Wyoming names no rear-facing age, though it does prohibit placing a rear-facing infant seat in front of an active airbag. So a Colorado parent can be cited for turning a one-year-old forward, while a Wyoming parent cannot. Pediatricians recommend rear-facing as long as the seat allows in both states, often past age 2, but only Colorado writes it into law.

The law that applies is the law of the state you are physically driving in. Colorado and Wyoming meet on I-25 between Cheyenne and Fort Collins and on I-80 across the south of Wyoming, one of the busiest commuter and freight corridors in the Mountain West. Because the booster and back-seat rules match, a family can follow one standard for older children the whole way: booster, in the back, until age 9. The only rule to add when driving in or moving to Colorado is rear-facing under 2, which Wyoming does not require.