On the North Fork of Yuba River. Now covered by Bullards Bar Reservoir. It was one of the earliest and best known diggings on the Yuba and was named for William Foster, a survivor of the Donner party. In April, 1848, Foster formed a partnership in a cattle ranch south of the Yuba River with his brother-in-law, Michael C. Nye. Foster was one of the first miners on the lower Yuba in June 1848. Foster had a store there and a claim to a large part of the bar in November 1848. The place prospered for a decade, first by mining with coffer-dams and after 1854 by the hydraulic process. In 1855 there were 300 inhabitants. In 1866 the post office was transferred to Bullards Bar.

- Erwin G. Gudde, 1975

"This famous bar is situated on the west bank of North Yuba between the mouths of Willow and Mill creeks. Mining in the Foster Bar township began here. William Foster, one of the original proprietors of Marysville, Charles Howell and Elijah, a civilized Indian, commenced mining below Rose Bar in June 1848. Early in 1849, Foster pushed up the stream and located at this point, which afterwards became known as Foster Bar. Here he worked for some time, employing Indians to assist him. When it grew later in the season a few miners wandered up the stream, some of them stopping at the bar. Still later in the season the bar became thickly populated by the many miners who had just arrived from the East."

" As soon as there was a demand for merchandise Foster opened a store. Early in 1850, Blake & Taylor opened a meat market, and soon other stores were established. The bar rapidly became populous and was the most thriving one in this vicinity. In 1850, a post-office was established here, and the bar was made the voting precinct for all the people in this region. In 1850, the population is set at various figures, ranging from five to twelve hundred. Both extremes may be correct, for in the winter season the population was largely increased by those who had been working in the surrounding country during the summer. The number of votes cast that year in the precinct was about fifteen hundred. There were several hotels, five stores, a number of saloons, gambling houses, butcher shops, blacksmith shops, etc. The leading hotel was the El Dorado, kept by the Atchison Brothers, who are well remembered as the most enterprising gentlemen of the town."

"A toll bridge was constructed across the river in the fall of 1850, by E.S. Gifford & Company. Gifford was a Quaker, and was killed by Indians in 1852. The bridge was carried away in the winter of 1850-1 by high water. It was rebuilt the next summer and again carried away that winter. James Stewart had an iron boat at this point that he used for ferrying purposes. Atchison & Rice constructed the bridge called Foster Bar bridge in 1854. The flood of 1862 raised the river fifteen feet. The river bed was filled up from fifteen to eighteen feet with tailings from the mines. In 1851, the town began to decline. The population was reduced to two hundred and fifty, and the number of stores to three. In the spring of 1850, the Foster Bar Mining Ditch Company and Star Mining Ditch Company undertook to turn the river, but failed. Afterwards the bed of the stream was worked by means of coffer-dams. The hydraulic mining kept the town on its feet for a number of years, but it became gradually deserted."

- Thompson & West, History of Yuba County, 1879