As growth moved south from Los Angeles in the 1950s, the Irvine Company, controlled since the 1930s by a nonprofit foundation, decided to develop its holdings. It was spurred by rising property taxes and the interest of the University of California in creating a new campus on the property.

The idea for a planned "new community" was first outlined by architect-planner William Pereira in 1960. He envisioned a "university-community," a college town of 100,000 residents on 10,000 acres, anchored by the University of California campus.

The campus, opened in 1965, became the focus for the ranch's southern sector master plan, which covered the 30,000 acres along the coast. It was approved by Orange County in 1964.

In the next few years, an in-house team led by Ray Watson and Richard Reese expanded the early Pereira work to encompass a community of half a million people on 60,000 acres. But the master plan they presented to the county in 1970 dealt only with land use and circulation. It included a detailed road hierarchy, but streetscape design and transit possibilities along activity corridors were limited to brief mentions in the text, drawing criticism from county planners.

The city of Irvine and other municipalities then took over, keeping the overall plan but reducing the intensity of development. An urban design study sponsored jointly by the Irvine Company and the city was produced in 1977 by the Philadelphia firm of Wallace, McHarg, Roberts & Todd. That study, along with the city's 1973 general plan, represented the increasing role of the public sector in the ranch's planning.

During my recent trips to Irvine, designers who had worked on the plans in the first decades described the Irvine Ranch to me as a large "canvas" for the latest innovations in suburban design. Diagrams from those early plans show careful consideration of different village layouts and an interest in the various scales at which people relate to the metropolis and region.

The village of Eastbluff, developed in 1964, featured some of the first attached housing in Orange County and a Radburn-like open space system. By 1975, when the village of Woodbridge opened, Irvine Ranch was actively marketing to nontraditional households.

The sale of the company to a consortium in 1977 led to the scaling back and dispersal of planning and urban design functions. Donald Bren, a member of the consortium, bought out most of his partners in 1983 and still owns the Irvine Company today.

Bren has increased the company's design capacity. The staff currently includes 10 landscape architects, five architects, and two planners. Bren's taste for classical and Mediterranean architecture and lavish planting are evident — a change from the earlier focus on California modern. While automobiles are still the dominant mode of transportation, housing and workplaces have become more tightly mixed than in the past.

In the late 1980s, environmental activism began to have a larger effect on the developers, leading eventually to the preservation of over half the ranch's open space.

Irvine Ranch's initial planning under William Pereira came from the mainstream of modernist design, and the 1970 master plan was a very broadbrush document. But because the development was so big, it soon became obvious that plans would have to evolve and that different concepts would come into prominence at different periods.

From my interviews with prominent planners and landscape architects who worked on the ranch in the 1970s, three features of the planning process stand out: the early influence of the work of MIT professor Kevin Lynch, the development's use of landscape to give identity at the site and district scale, and its approach to open space protection.

Among those influenced by Lynch were Ray Watson, who headed planning until 1966, and then headed land development and finally the company, and Richard Reese, the head of planning.

In his 1960 book, Image of the City, Lynch said that it was possible to detect a shared image of the city. Drawing on his studies of the spatial perceptions of residents of Los Angeles, Boston, and Jersey City, he suggested that some environments are more legible ("imageable") than others.

To analyze environmental legibility he came up with a vocabulary of city elements, the well-known paths, edges, districts, nodes, and landmarks. Irvine Company planning documents from the 1960s to the current period have stressed creating identifiable districts, defining edges, and creating landmarks.

A city where people can easily identify these elements has more possibilities for "collective memory," Lynch said, and for "wayfinding." The distinctive visual character of each village as well as key landmarks help people find their way around.

Today, the Irvine Ranch's restrictive architectural covenants help to bolster the distinctive character of each village. But the covenants also reduce the potential for positive change.