Orange County formally separated from Los Angeles County in 1889, and there's been no looking back. Wilderness gave way to rich farmlands, where oranges, lemons, avocados, and walnuts made agriculture the new county's most important industry; the region was actually named for the prevalence of its citrus groves. The 20th century brought with it plenty of entrepreneurs, including Walter Knott and later Walt Disney, along with the aerospace industry,...