HISTORY BOOKS in the 1950s, Frances FitzGerald points out in her latest book, portrayed America as a homogeneous nation. History texts of the next decade, however, taught that American society wasn't--and never was--homogeneous and that the U.S. was more of a "stew" or "salad" than the "melting pot" of lore.

Cities on a Hill

By Frances FitzGerald '62

Simon and Schuster; 414 pp.; $19.95.

But not all groups have been content to live with in the American salad bowl. In Cities on a Hill, FitzGerald--who is running this spring for a position on Harvard's Board of Overseers on a University-nominated slate of candidates--takes the reader through four alternative communities that popped up in America during the past two decades: the Castro, San Fransisco's gay neighborhood; Lynchburg, Virginia, home of Jerry Falwell's Liberty Baptist Church; the Rajneeshee community in Oregon; and the Sun City retirement village in Florida.

The only thing that these four communities have in common is what motivated their creation. Each was set up as a new utopia, a new city on a hill for the people who had the vision to build them. In no other nation, FitzGerald writes, have people so confidently felt that "they can start all over again from scratch...that they can reinvent themselves." This attitude, she argues, is quintisentially American.

FITZGERALD combines smooth writing and keen journalistic observation in her tale of four such attempts by contemporary Americans to start all over again. FitzGerald's best chapters are the ones exploring the Castro and Sun City. We witness the excitement and joy of the gay community as social values relax enough so that they can "come out of the closet" and settle in one place--their place--to live and to start over. FitzGerald takes us into the life of their community, from its parades to costume balls. With her, we take part in their joyous spirit of release.

We also feel their pain and shock when Mayor Frank Moscone and Harvey Milk, a homosexual aide, are assassinated by a crazed, homophobic ex-cop. Then we are exposed to their deathly fear of AIDS and its effect on their community:

The Castro had become something like the Algerian city of Oran that Albert Camus described in The Plague--a city separated from the outside world, where death and the threat of death hung over everyone. Very often they [AIDS victims] were athletic, ambitious, good-looking men who one day found a purple spot somewhere on their body. The purple spot was the nightmare that haunted the sleep of the Castro. Waking up in the morning, men would search their bodies for it; not finding it, they would search again the next day. Those who found it went on to a new series of nightmares.

Fitzgerald's tour of Sun City is equally fascinating. She sees Sun City--and other retirement villages like it--as the most radical of the communities discussed in her book. "Never had older people taken themselves off to live in isolation from younger generations," she writes. Senior citizens living in Sun Cities across the nation are on the "cutting edge" and living well into their eighties. She writes:

In a sense, the residents of Sun City Center and their peers across the United States are living on a frontier. Not a geographical frontier but a chronological one. Old age is nothing new, of course, but for an entire generation to reach old age with its membership almost intact is something new. Until this century, death had no more relation to old age than it had to any other period of life. In fact, it had less.

IN HER introduction, FitzGerald recalls that America was founded by visionaries such as John Winthrop, who told his Puritan followers that they were creating a city on a hill and that the eyes of the world would thus be upon them. "The remarkable thing," FitzGerald concludes, "was that four centuries later Americans were still self-consciously building cities on a hill." And thanks to her, we are able ourselves to view them.