As former L.A. Times’ reporter Evan Halper explained in his excellent “United States of California” series, you would be hard pressed to find another state that has influenced the nation more than the Golden one.

“No state has had a bigger impact on the direction of the United States than California, a prolific incubator and exporter of outside-the-box policies and ideas,” Evan wrote in introducing his stories.

So, how did California become America’s think tank?

A great new book takes a stab at answering that question. John Mack Faragher, a retired Yale history professor, has just published “California: An American History,” which explores how the state became the most populous, diverse, economically dynamic and confounding state in the union. Kirkus calls the book “a masterful history of a place that is both reality and ideal, and central to the modern world.”

Here are some lightly edited excerpts of my recent interview with Faragher (oh, buy his book):

Can you sum up California in one word?

Diversity.

Geologic complexity produced a patchwork of local ecologies. The state’s Department of Fish and Wildlife lists 178 major habitats, more than any other state, populated by over 5,000 plant species and at least 1,000 animal species, many living no where else.

This natural abundance supplied the means for the growth of the largest Indigenous population of any region in the U.S. Native Californians lived in hundreds of communities of astounding cultural variety, speaking at least 78 distinct languages. Today the federal government recognizes 109 California bands and tribes, more than any other state.

Human diversity is the foundation of California history. The 22 adult men and women who founded the pueblo of Los Angeles included two Spaniards, two men of African descent, nine Mexican Indians, and nine individuals of mixed Spanish, African and Native ancestry

The gold rush drew men and women from every state in the union — Black and white, free and slave. Thousands more came from Mexico and elsewhere in Latin America, the Pacific Islands and Australia, China and Europe. A powerful migration from the Midwest began around the turn of the 20th century and extended into the 1920s, followed by a flood of displaced farm folk during the Depression.

With World War II, that tide became a tsunami. During the last two decades of the 20th century, powerful immigrant streams from Latin America and Asia brought millions more. Today, California’s 40 million residents make up the most diverse population of any state.