Why were "bath salts" for sale in head shops? Because they contained stimulants known as substituted cathinones that can affect user behavior and judgment. They've been growing in popularity as a legal alternative to cocaine or methamphetamine.
As of April 15th, they're no longer legal in Washington; the state Board of Pharmacy has approved emergency rules classifying the salts as Class I controlled substances, banning their manufacture, sale, delivery and possession.