Child restraint requirements differ for the various states in the United States.In Florida and South Dakota, children who are four years or older can use an adult seat belt without a child safety seat. In the rest of the country, a booster seat or otherwise appropriate child restraint is required until the child is between five and nine years old, depending on the state.Most states include in their law a requirement that all infants ride rear-facing until they are BOTH one year of age AND at least 20 pounds. Though it is not included in every state's law, no child safety restraint marketed to the US will accommodate an infant less than 20 pounds, some no less than 22 pounds, in a forward-facing position. As of 2011, most children ride rear-facing until they are at least 2 years of age.The National Highway Traffic Safety Administration (NHTSA) advises the use of a child restraint or a booster seat for all children who are shorter than 4 ft 9 in, regardless of age and weight, or even longer if the belts hit the child at the wrong place. Some booster seats can be used for children up to 60 inches and 120 pounds.Many state laws prefer that children 12 years and younger sit in the back seat if available. Some states, as is the case in Michigan, forbid placing a child under the age of 4 years in a front seat if a rear seat is available.Some states require that all child safety seats be used in full accordance with the manufacturer's instructions in what is sometimes referred to as a "proper use clause".