Last week we took note of a demographic milestone, as the estimated U.S. population zipped past 300 million, just 39 years after hitting the 200 million mark.

We've attracted quite a crowd, all right, and these few years of breathtaking growth have wrought remarkable changes in the American way of life.

Two-and-one-half times as many automobiles clog the nation's roads than were registered in 1967. They've carried with them profound consequences for the environment, highway safety, and our already-impatient state of mind.

Back when we were a nation of 200 million people, 38 percent of us lived in the suburbs. Now fully HALF of our 300 million people do. Housing tracts have displaced pastures and quiet copses and turned suburbs into centers of economic and political power. And everything you may have heard about explosive growth in what we call the "Sun Belt" is true. Just about half of our 300 million people now live in the sunny South and West. That's twice as many people as lived there 39 years ago.

In that span, the percentage of women in the workplace has swelled from about 40 to almost 60 percent. And the percentage of older Americans has nearly doubled. Since a lot of old folks live alone, that has steadily shrunk the typical American household size.

Back in 1967, young adult Americans could hardly have guessed that by the time they retired, 100 million more people would crowd around them, or that those days -- already fast-paced, complex, and abuzz with technological change -- would be looked back upon as a slower, simpler, even sweeter time.

More essays in Ted Landphair's Only in America series