What is "municipals"

Usage examples of "municipals".

He had his broker arrange a negotiated sale through the floor specialists, and he put the tax money aside in treasury bills, and he stuffed the rest of it into tax-free municipals, and there he was all of a sudden with a tax-free income coming in on the basis of like two hundred and forty dollars a day forever, and it was money he didn't have to touch because what was coming in from all other sources was more than sufficient to his needs, even in Garden Suite Number Five in Tropicana Grove Retreat.

We turned up a lot of information on petty crimes, none of which was of the least interest to us--do you want me to pass it on to the municipals, by the way?