HOUSTON — A funny thing happened here on Friday. Texas came to town.

Cowboys and cowgirls were everywhere — on the sidewalks and in the playgrounds, in the downtown skyscrapers and the restaurants — and they were not even tourists. They actually lived here.

For decades, this city has celebrated, as it did on Friday, a tradition called Go Texan Day, the one day of the year on which people in Houston dress the way people outside Houston think people in Houston dress. On the Friday before the annual Houston Livestock Show and Rodeo gets under way, tens of thousands of Houstonians head to their schools and offices in newly purchased cowboy hats, cowboy boots and jeans. They dress, in other words, as if they’re from Texas, which they are, though it is easy to forget that simple fact in the state’s biggest city.