It didn’t seem like a "Eureka!" moment. But in 1873, when Eliza Tibbets planted two Bahia navel orange seedlings in Riverside, she set off California’s citrus gold rush. Today, as old orchards vanish, the California Citrus State Historic Park in Riverside preserves 186 acres of orange, lemon, and grapefruit trees. Visit the park’s museum and a grove that showcases 75 citrus varieties. In the gift shop, thumb through posters of vintage labels and you’ll see that citrus-era California was a land where money and dreams grew on trees. Information: (951) 780-6222, www.parks.ca.gov.