Current U.S. Bicycle Helmet Laws
There is no federal law in the U.S. requiring bicycle helmets and no state has a universal bicycle helmet law. Twenty-one states and the District of Columbia do have statewide bicycle helmet laws that apply to young riders (often riders younger than 16). There is no bicycle helmet use law in 29 states.
Some 152 municipal localities have enacted age-specific ordinances that require bicycle helmet use, typically these laws cover bicyclists under age 16.
Fourteen states have no statewide or local helmet laws. These states are: Arkansas, Colorado, Idaho, Indiana, Iowa, Minnesota, Mississippi, Nebraska, North Dakota, South Dakota, South Dakota, Utah, Vermont and Wyoming.
Bicycle Helmet Use Laws by State

Blue: State-wide bicycle helmet use law
Red: Some local bicycle helmet use laws
Gold: No known local or state-wide bicycle helmet use laws
Sources for Further Information on U.S. Bicycle Helmet Use Laws
The National Conference of State Legislators (NCSL) has partnered with the National Highway Traffic Safety Administration (NHTSA) to develop a traffic safety legislation database that can be accessed at www.ncsl.org for an update on current bicycle safety legislative action by states and localities.
Source for Further Information on Laws Concerning Bicycling by State
MassBike at www.massbike.org/bikelaw/statelaws.htm maintains by state a compendium of links to state, provincial, and local laws that address the motor vehicle code, licensing, registration, bicycle equipment, rules of the road, safety standards, races, violations, and penalties, etc.