What was going on when I was born?

AMERICANS have always loved Americana but never more so than in recent years, and that is one reason why New York's Fall Antiques Show, which opened yesterday with its focus on American furniture and artifacts, has become in just four years one of the most important and popular antiques events in the United States. But popularity has its drawbacks, particularly for antiques. It can create a market that is lean on quality and long on predictability. It is a tribute, therefore, to the 90 dealers now assembled at the Passenger Terminal at Pier 88 at West 48th Street and the Hudson River that this year's show is filled with first-rate pieces in nearly every category. And it is nothing less than a triumph of showmanship that the Queen Anne highboys, Amish quilts, painted wedding chests and folk-art weathervanes look so witty and fresh even after all these seasons at center stage.

Sales of new single-family houses rose a slight 2 percent in August, continuing a seesaw performance that has left sales at almost exactly the same level as a year earlier, new Government figures indicated today. Prices continued to rise, hitting a record median of $73,200 for new houses sold during the month, up from $71,800 in July, according to the report from the Commerce Department and the Department of Housing and Urban Development.

Secretary Richard S. Schweiker of the Department of Health and Human Services told the Carey administration yesterday that he intended to approve New York's proposal for a unified system of hospital reimbursement for the state, one that would create a fund of hundreds of millions of dollars for the hospital care of the uninsured poor. However, Mr. Schweiker established a number of conditions for Federal approval that state health officials in Albany said they were not sure could be met. According to the officials, the conditions, while not onerous, removed some of the financial benefits New York wanted.

While all six defendants in the Brink's murder trial face charges of murder and robbery, the legal approaches they have taken in their cases are as dramatically different as their decorum in the courtroom. Four of them, Nathaniel Burns, Donald Weems, David J. Gilbert and Judith A. Clark, contend that the proceedings are fundamentally illegitimate and illegal - ''part of the government's armed apparatus of war to maintain power and domination,'' Miss Clark has said. After several disruptive courtroom appearances, they are now refusing to participate in the preliminary hearings, and seem likely to sit out the trial as well. To Kathy Boudin and Samuel Brown, however, the Rockland County proceedings represent their only hope of avoiding lifetimes behind bars. Quiet and intense in court, they are nonetheless contesting their cases vigorously.

The Tsoung Shing Coffee Shop - a little bit of China in the center of Queens - is a place of many beginnings. It officially opened three years ago, but its roots date back far longer - to the streets of Hong Kong and a man named Ming You, who left his home and pregnant wife to make a fortune in New York. Mr. You never did make that fortune. In fact, it took 19 years before he earned enough money to send for his wife and the daughter he had never seen. But it is that daughter, 35-year-old Tina Wong, who stands behind the counter these days at the Tsoung Shing - a combination coffee shop and Chinese restaurant where the cornflakes sit alongside the ginger hot sauce and scrambled eggs share plates with the pork fried rice. It is the kind of place that will never make a fortune for anyone, but that an entire family calls home.

First there were commodity futures contracts. Then there were stock options. Now, starting today in New York and Chicago, there will be options on commodity futures. Most commodity experts readily concede that commodity options will add to the complexity of an already tangled web of financial investments. But they predict that individuals with a speculative bent will flock to the new contracts, where they can seek the huge gains for which commodity markets are noted but avoid the equally dramatic losses that commodity traders often suffer. Unlike the futures markets, where traders have virtually unlimited risk, option buyers never stand to lose any more money than the price paid for the option, known as the premium. In the world of commodities, a market where one can lose no more than one's entire investment is considered low-risk.

The Southeast Banking Corporation yesterday gave up its seven-month struggle for control of the Florida National Banks of Florida and agreed to swap a 23 percent stake in Florida National for assets. Under the agreement, Florida National will give Southeast, the state's largest bank holding company, 25 banking offices and related real estate in return for 1.7 million of its own shares, plus cash. The cash and stock are valued at about $80 million.

Because of an editing error, an arti- cle Saturday incorrectly identified George Gregory Korkola, who is being extradited from Spain on charges re- lating to illegal arms dealing. The ar- ticle should have identified Frank E. Terpil, not Mr. Korkola, as a former Central Intelligence Agency agent.

''There is no contradiction between permanent peace for Israel and the legitimate rights of the Palestinian people.'' - Secretary of State George P. Shultz. (A10:1.)

IN case you hadn't noticed, the new season in the galleries starts just a week or two before the first leaves turn red. It's a jumpy, unfocused sort of time - a moment at which no one knows quite what to expect. Contrary to what is sometimes thought, the New York galleries are not at all standardized. The better they are, the more individual they are. Contrary (once again) to what is sometimes thought, the best galleries are always looking for the new and the good and doing their best to bring it to fruition. They don't forget the old and the good, either, and the first day of October is a good time to see what comes of it all.

Control of Canada's largest independent oil company, Dome Petroleum Ltd., is passing to the federal Government and four of the country's biggest banks as a result of a bailout agreement that provided Dome with $1 billion (Canadian). Until now, Dome has been dominated by John P. Gallagher, chairman of the board and chief executive officer, who started Dome 32 years ago and built it into Canada's largest oil company. He is now Dome's largest single shareholder, with about 4 percent of the stock. The agreement, still subject to approval by the Parliament and by other creditors, gives the four Canadian banks and the Government the right to name a majority of the members of Dome's board, whose 10 current members are loyal to Mr. Gallagher and William Richards, the president.

A United States marine was killed and three others were wounded today as undetected explosives were ''accidentally detonated'' at Beirut International Airport, an American military spokesman announced. The explosion came on a day in which President Amin Gemayel declared that Beirut was now a unified capital and no longer divided into a predominantly Moslem West and a predominantly Christian East. The casualties, the first suffered by the Americans during their peacekeeping duties here, occurred on the second day of the deployment of 1,200 United States marines at the airport. The last of the marines assigned to the multinational peacekeeping force here landed on a nearby beach today to bolster the 800 who arrived Wednesday by ship and helicopter minutes after Israeli troops left the area.