Los Angeles

Los Angeles spreads across a vast coastal basin in Southern California, hemmed between the Pacific Ocean and a ring of mountains — the San Gabriel and Santa Monica ranges — that trap both the city's sprawl and its smog. The second-largest city in the country, it anchors a metropolitan region of more than 13 million. The Los Angeles River, mostly a concrete flood channel today, once watered the original Spanish pueblo founded in 1781.

The basin's Mediterranean climate — warm, dry summers and mild winters — and its flat, buildable land encouraged a low, horizontal city that grew outward rather than upward, knit together by freeways. Mountains rise abruptly at the edge of the plain, snow-capped in winter within sight of the beaches. The region sits astride the San Andreas and related faults, making earthquakes a permanent fact of life.

That geography — ocean, basin, and mountains under near-constant sun — made Los Angeles the capital of the film industry and a sprawling magnet for migration through the 20th century. Water piped from hundreds of miles away sustains a metropolis the local rainfall never could. It is the dominant city of the southern half of the American West Coast.