What is the greatest height allowed by state law a vehicle including its load?

There's no single answer to the greatest height allowed by state law for a vehicle including its load. Each US state (and other countries) has its own regulations regarding vehicle height limits. These limits often vary slightly and may depend on factors such as the type of vehicle and the specific roadway. You would need to consult the specific state's Department of Transportation (DOT) website or regulations for that information. The limits are typically around 13.5 to 14 feet, but this is not universally true.