After Texas joined the United States and Mexico ceded it, along with the area known as Medio México or the trans Nueces, things begin to settle down in the frontier. Gradually, the area began to take form in the mold of other parts of the new country.
On February 1, 1858, the Texas Legislature created 23 counties including Duval County. Many historical references suggest that Duval County was formed from parts of Nueces, Starr and Live Oak Counties. The law that created Duval County makes no mention of this point. It merely laid out the county’s boundary, which did not mention either Live Oak or Nueces Counties.
To be sure, the boundaries laid out in the law were somewhat ill defined. The confines of the new Duval County started at the southwest corner of the newly created McMullen County and proceeded east for six miles. From there it proceeded south to the northeast corner of Starr “or” Hidalgo Counties. Then it followed a northeast line to just south of the southeast corner of another newly formed LaSalle County and the southwest corner of McMullen County and then east to point of beginning.
The county was named in honor of Burr H. Duval who fell at Fannin’s Massacre in Goliad. A number of sources suggest that the county was named for Burr H. Duval, John C. Duval and Thomas H. Duval, but the law creating the county only names Burr H. Duval.
The law mandated that the county seat would be within 10 miles of the center of county and was also to be named Duval. The statute went into great detail on how this was to be achieved. A survey was to be made of the county with a dot drawn at its center and a circle drawn around the dot indicating a distance of five miles from the center. Three sites were to be selected within the circle and an election was to be held to determine which would be the location for the county seat. This, of course, never occurred as San Diego was chosen as the county seat and as is commonly known it is on the eastern edge of the county with part of it, at that time, being within Nueces County.
The law creating Duval County also spelled out how it was to be organized. When 75 “bona fide free white male inhabitants” petitioned the Chief Justice (County Judge) of the adjoining county or the nearest organized county, the Chief Justice was to call an election to select county officials. Until such time as the county was organized it would be attached to nearest judicial district for purpose of administering the laws of the state and nation.
It was not until April 22, 1876 that N. G. Collins, P. C. Gravis, J. W. Moses, and other citizens petitioned the Nueces County Commissioners Court for recognition. Nueces County denied the request because commissioners were not sure if San Diego, from where most signatures were from, was in Duval County or Nueces County. It took three more petitions before the Nueces County Commissioners called for the mandatory election to organize Duval County.
 Gammel, Hans Peter Mareus Neilsen. The Laws of Texas, 1822-1897 Volume 4, Book, 1898; digital images, (http://texashistory.unt.edu/ark:/67531/metapth6730/ : accessed July 30, 2013), University of North Texas Libraries, The Portal to Texas History, http://texashistory.unt.edu; crediting UNT Libraries, Denton, Texas.