San Joaquin county was one of CA's "original" counties.See URL
for info for diffrent eras.You're problem may be that there was a lot of "boundary adjustments" per below.
Creation of Townships
Soon after California's admission into the Union, September 9, 1850, the Government sent out surveyors to divide the state into townships and sections. Each township was six miles square and each section one mile square. In locating the east and west base line of the central part of the state the surveyors selected the highest peak of Mt. Diablo as their starting point and this line runs due east through French Camp to Trigo, a small railroad station on the Oakdale line of the Southern Pacific. The Court of Sessions in defining the boundaries of the three townships, O'Neal, Castoria and Elkhorn, created by them, gave no attention to the township area of the Government surveyors. In fact it was not necessary to limit a township to six square miles as outside of the townships named the county was scarcely inhabited.
O'Neal township, created in 1853, was so named after John O'Neal, a popular southern man and sheriff of that day. The township embraced the whole of the Weber survey, El Campo de los Franceses and nearly all of the swamp and overflowed land to the west. Then it was a vast area of tules and the home of wild game. To-day, much of it reclaimed, it is the richest fruit and vegetable raising land in the state.
Castoria, a Spanish word, meaning beaver, was also created in 1853. It took in the entire county south of the base line. Its bounds were the San Joaquin River on the west and it extended to Knights Ferry on the east with the Stanislaus River as its southern boundary. At the present time Lathrop and French Camp are within its bounds.
Elkhorn township was also created by the Court of Sessions, 1853. It was so named because of the large quantity of elk horns found in that locality. The township, like that of Castoria, was exceedingly large.North of the Weber survey, it extended east from the Mokelumne River to Calaveras County, with Dry Creek its northern and the base line its southern boundary. Lodi and Woodbridge to-day are within its bounds. The township is famous for its wonderful grapes and bounteous supply of fruits.
Elliott township was established in 1855, the supervisors cutting off the entire eastern half of Elkhorn township to form the new territory. Its bounds were the same as those of Elkhorn, except on the west. The division was made at the request of the settlers in Lockeford, for that town and Woodbridge were rivals for business and township honors. Within the present township are Lockeford and Clements.
Tulare, probably named because of its immense tule growth, was created in 1856. The reasons for its being set aside as a township I cannot imagine, unless it be that John Westley Van Benscroten was anxious to make Grayson a prominent township village. The township included all of the land within the county west and south of the San Joaquin River. Irrigation of the sandy land and reclamation of the swamp land is now making the section very productive. In this township lies Tracy, Banta, Vernalis and San Joaquin City. The territory in which Grayson is situated was given, in 1860, to Stanislaus county.
Dent township was created by the supervisors, February 17, 1859. It was named after George W. Dent, a resident of Knights Ferry and a brother-in-law of Captain U. S. Grant. The township was formed by cutting off the east half of Castoria and the south part of Elliott township. This formed a township nearly twelve miles square, with the Stanislaus River as its southern boundary, Calaveras County its eastern and Douglas township—created at the same time—as its northern boundary. The following year, 1860, the legislature, slicing in half Dent township, and taking a part of Douglas township, gave it to Stanislaus County. The division included the town of Knights Ferry, then a prosperous town of over a thousand inhabitants, and the act was one of the many political tricks of that day. Ripon, Burwood and Atlanta are the towns of Dent township.
Douglas township was named in honor of David F. Douglas, senator from the San Joaquin district. The township was created in 1859. In forming the township the supervisors cut off the southern part of Elliott township. It is bounded on the north by Elliott, east by Stanislaus County, south by the base line and west by the Weber survey. The legislature in giving additional territory to Stanislaus County in 1860 also took a part of Douglas township. Within this district lie the towns of Peters, Linden and Farmington.
Liberty township was created at the request of many residents in that section in June, 1861. As the territory then was all allotted the new township was carved out of the northern portion of Elliott. The only town is Acampo. There was a town founded and prospered for a season called Liberty, but the establishing of a railroad station at Mokelumne City ruined the after prospects of Liberty.
Union, the last created township, was formed in May, 1861, from the western part of Elkhorn township. The original territory was largely swamp and overflowed land, but now reclaimed; the passing through of the Western Pacific Railroad made this rich land very valuable. Land is valuable principally for resident or productive purposes and no land can be of value unless given cheap and quick transportations to market.
Staten Island township comprises one of the soil-richest islands in the state. It lies between the west and south fork of the Mokelumne River, the west fork of that river being the boundary line between Sacramento and San Joaquin County, according to the original Gibbs survey of 1850. Along in the middle '70's Staten Island, having been reclaimed, Sacramento was very anxious to annex the island to that county for as was stated later it contained 7,000 acres and was assessed at $14 per acre. By some political "hocus pocus," as the Independent expressed it, they succeeded in getting the legislature of 1876 to annex the island to Sacramento County. The island by nature and the original county law belonged to San Joaquin County and the residents of the township were quite wrathy over its loss. One reason of their anger was that it compelled the residents on the island to cross the Mokelumne River and travel to Sacramento for all official business. At the following legislature, in 1878, Assemblyman Ross C. Sargent of San Joaquin introduced a bill, which passed, reannexing Staten Island to San Joaquin County. The legislature only performed their duty and corrected a wrong, but some of the citizens of the Capital, peeved at the result, strongly censured Assemblyman Grove L. Johnson, father of Hiram Johnson, for not preventing the passage of the bill. Johnson in reply said, "I got the bill referred to the Sacramento and San Joaquin delegation and then getting possession of it, I locked it up in my desk and kept it there until Sargent threatened to introduce a resolution demanding me to report it." Johnson by this trick kept the bill secreted for nearly two months and then San Joaquin came into its own.