KKAR were the original call letters. It was a daytimer and here's a print article around the time of launch:
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And here's what it sounded like:
Hey, at the time, Pomona was 70,000 people. There was a decent local advertising base, and being 30 miles from both Los Angeles and San Bernardino, people who lived there probably didn't identify with either of those two cities and wanted and needed a local station. But we saw the business case for suburban stations buried in major markets pretty well evaporate forty years ago.
71.4 % of Pomona's population is Hispanic or Latino, according to the 2020 Census. That's 104,958 people out of 147,000.
Important distinction: Only 32.7% of Pomona's residents are foreign-born---from
any country. That's 48,069.
Even if ALL of them were Hispanic or Latino, that leaves 56,889 Pomona residents who are Hispanic or Latino who were born in the United States of America. And that 56,889 is 38.5% of Pomona's population.
The non-Hispanic White population is 10%. That's 14,700. Only 35% of the city's households report English as the only language spoken in their homes.
If KTMZ was able to make money with Spanish-language programming until recent events, and they're not now, then that's not "it wasn't successful", it's a change in the available audience sparked by external forces.
I expect we will see more, but I also expect that those that can continue to make money with Spanish-language programming will do so. Any format change is expensive. Changing languages virtually guarantees your audience will drop to zero rapidly and then you're in the situation of attracting a new one. And in a crowded media market like Los Angeles, that's tough with a city-grade signal and a healthy budget---something few of these stations possess.