Julian Smart did not come to the Tuolumne River looking for gold. He came to grow things. In the spring of 1849, while prospectors tore at the Sierra foothills with picks and pans, Smart planted a garden and an orchard along the riverbank at an elevation of 800 feet. He named his settlement after Colonel A. M. Jackson and set about supplying the one thing miners needed almost as much as luck: food. The Tuolumne River provided water for his crops and for the mining operations that proliferated around him. Jacksonville quickly became one of the largest towns on the river, a trading post with several stores, a post office that opened in 1852, and three hotels that passed for luxury on the frontier. Estimates of placer gold recovered from the Jacksonville district vary wildly, from nine million to forty million dollars in period value. Smart had planted himself in the right place at the right time.

As surface deposits played out, the district shifted from panning to hard-rock mining. Starting in the late 1850s, lode mining began tunneling into the hills around Jacksonville. The Eagle-Shawmut Mine, first discovered in 1850, operated on a massive scale from 1897 until 1942, becoming the single most productive gold mine in Tuolumne County. It sat at the heart of the Mother Lode, that great belt of gold-bearing quartz that stretches through the western Sierra Nevada foothills. Even after the initial frenzy faded, Jacksonville continued to function as a small country town through the early twentieth century, its population modest but its roots deep in the landscape. Generations lived and died along the Tuolumne, their stories layered into the soil like sediment.

The original Don Pedro Dam, completed in 1923, already changed the river's character, but the town survived. When engineers decided to build the New Don Pedro Dam 250 feet higher than the old one, Jacksonville's fate was sealed. Between 1967 and 1971, the town was razed. Buildings were demolished. Roads were abandoned. The rising lake submerged the old dam on April 12, 1970, and by June, the water had swallowed Jacksonville entirely. The new reservoir held over two million acre-feet of storage, enough to supply irrigation across the Central Valley and generate hydroelectric power for the region. The cost was measured in more than concrete and steel. An entire community, its streets and foundations, its orchards and mine shafts, vanished beneath a deepening lake.

On November 19, 1971, a historical marker was dedicated at the northern approach of the Don Pedro Bridge, placed by the Sonora Rotary Club and the Tuolumne County Gold Centennial Committee. California Historical Landmark No. 419 stands on a vista point along State Route 120, three and a half miles southeast of Chinese Camp, marking a town that cannot be visited. In drought years, the reservoir drops low enough to expose fragments of what lies below: mining equipment, bridge pillars, the bare outlines of a settlement that once fed and supplied the Mother Lode. Then the rains return, the water rises, and Jacksonville slips back under. The town exists now as a cycle, appearing and disappearing with the weather, a reminder that Gold Rush California built quickly, prospered briefly, and sometimes drowned in the name of progress.