By Susan Guerrero

My grandfather often spoke to me of the old-fashioned knock-down, bang-up Sept. 16ths of his boyhood, when every town in the Arizona Territory shut down and everybody celebrated, Mexican and Anglo, just like on the Fourth of July.

He was the son of a famous 16th of September orator and proud of it, although he was just a baby when his father made his last long speech from the back of a flag-draped wagon.

He often asked me why we didn't celebrate the 16th of September anymore, but I had grown up in Connecticut and had no idea. "I guess they just forgot," he would say sadly.

Because of him, I think of Sept. 16 not as the day Mexico handed Spain her hat, but as the day of forgotten Mexican American history. It wasn't only the vanished holidays that had somehow congealed into a weeklong supermarket celebration of Cinco de Mayo that upset Tata. He felt that Mexicans were being left out of the history of the Southwest.

He was not as well educated as his father, going no further than the third grade at a ranch school, and he was an awkward writer. But he was an eloquent speaker, having inherited his father's gift for oratory and trained in it by diligent attendance at his local Toastmasters club.

These are Tata's notes for a speech he gave in 1972 at for the historical society in Florence, Ariz., a town he had known well as a boy:

"My interest not only of Arizona history as a whole, but of Mexican American participation in particular. I find where we have lacked so very much writers, who gave Mexican American pioneers very little mention, if any at all. Yet Florence was a half and half population of Anglos and Mexicans.

"In researching, mostly from old-timers, I can cite that we had quite a number of prominent men in many fields, but history books that I have been able to acquire mention none, at least in Florence. In making reference where events and men are concerned, they read Jack Brown and Jim White and a Mexican or two Mexicans. Bob So and So owned the ranch or farm and had a Mexican for a neighbor. Johnny Du Vois called Soft Drink Johnny came to Arizona in 1876 as a stage driver -- married a Mexican woman. DOES NOT MENTION THE NAME OF THE WOMAN'S FAMILY." As he would say, it burned him up.

Even today, the historical society -- to which he was devoted -- has the standard "O Pioneers" kind of exhibits, reproduced in a thousand dusty little museums all over the West and Southwest. There are arrowheads and pottery to represent the Indians, and guns and saddles to represent the cowboys. And to represent the ladies, a bonnet or two, a washboard and a sunburned piano or, in Florence's case, the exhausted-looking organ that Tata's mother played at the Presbyterian church.

There is nothing there, unless fingerprints count, to recall her or any other of the town's many Mexican settlers.

In any event, Tata had his own museum, a memento-filled cabinet in the guest room of his house. The museum -- that is what he called it -- had five or six shelves of souvenirs: a clay bust of him by a grandson, a Barry Goldwater lighter, a key to the Playboy Club, hospital I.D. bracelets, seashells, rocks, a rusty spur, ashtrays, matchbooks, cheap plastic trophies, campaign buttons and pill bottles full of soil from the many places he had been, including one that said "unknown," all symbolic of some event, time or trip he did not wish to forget.

As he grew older, he turned his attention to another kind of remembering, making tombstones for his friends who could not afford one, troweling concrete into a wooden form so that they would not lie in unmarked graves.

He also collected photos by the dozens of Mexican Americans he had known in territorial days, their houses and the buildings that they had owned, which he kept in a locked, fireproof room off his bedroom.

Over time, I became familiar with the La Familia Cruz and the Armentas and even with the Lopez sisters, grim-looking in their Gibson girl shirtwaists, who, Tata said, would do all kinds of things with young men under such-and-such a bridge, "especially Adela." So much history had been lost that Tata was anxious not to lose one more speck, even if it meant besmirching a woman's name.

His collection of photos of now melted adobe buildings included a general store in Casa Grande, Ariz.; its owner, Gin Lung; and his brother, Fatso Lung. When I asked Tata how Gin Lung and Fatso Lung, who were from China, got into a collection of photos of Mexican American pioneers, he said: "Because my mother probably owed Gin Lung money when she died. And because they had no one else."

Susan Guerrero is a staff editor at the New York Times.