The Mercurio Martinez Papers (1797-1963 (bulk: 1910-1963)) include correspondence, copies of legal documents such as wills, deeds, affidavits and courtroom briefs, maps, a few photographs, field notes for land surveys, genealogical charts, accounts of family and regional history by Mercurio Martinez, and historical accounts from other sources, principally newspapers. There are also financial records of various kinds including tax records, bills and receipts, books of check stubs and account sheets.
The vast majority of the papers relate to families, places and events in Zapata County. Webb County is also well represented, as is the region surrounding the town of Guerrero, Tamaulipas located on the south bank of the Rio Grande opposite Zapata County, Texas. A few papers deal with families, places and events in Starr County and further south in the Rio Grande Valley and a few files deal with Mexican, United States and world affairs. Unless otherwise noted in the inventory, files deal with Zapata or Webb County matters.
The oldest original papers date from the latter part of the nineteenth century and include such documents as Mercurio Martinez's Texas Teachers Certificate, 1898 (Series 1-3/4); a General Land Office map of Zapata County, 1885, (Series 3-14/25); and a certificate appointing Proceso Martinez, Sr., Mercurio's father, to the Zapata County Board of Appeals, 1870, (Series 3-25/23). There are also copies and translations of nineteenth-century documents including partition deeds, deeds of sale, birth records, and maps. Accounts of family and local history written by Martinez in the 1950s and early 1960s deal with events dating back to the Spanish settlements along the lower Rio Grande in the 1750s. Genealogies are generally traced back to the first colonists to arrive in the region. Family records, therefore, cover a time span of more than 200 years, from the settlers who arrived on the banks of the Rio Grande in about 1750 to their descendants in the early 1960s. Each decade from 1900 onward is represented in the papers. There are more files from the 1950s than any other single decade.
Among the most important files in the collection are those on the relocation of the town of Zapata due to the construction of Falcon Dam on the Rio Grande in the early 1950s, the salvation of the community of San Ygnacio from destruction during this period, the accounts of family history and genealogy from Zapata County, and the papers related to the division of lands between descendants of original holders of Spanish grants and sales of family lands. Maps, genealogies, and legal documents provide a clear picture of the rapidity with which even extensive landholdings can be reduced to tracts hardly adequate to support the families of the grandchildren and great-grandchildren of the original owners. Reconsolidation of holdings through the purchase of interest from siblings and through cousin marriage are also documented. It is also possible to trace shifts in settlement and land-use patterns. For example, the original grantees of porciones along the Rio Grande held land in long narrow blocks extending inland from the river. Over the generations, these blocks were subdivided among heirs and parts of them were sold outside the families. Through separate inheritance from parents, through marriage, and through purchase, individuals came to own small pieces of land located in widely separated tracts. This pattern of dispersed holdings, each of economically inefficient size and too far apart to be worked as units, has been noted for many peasant societies. These papers clearly reveal the processes whereby such a land-holding pattern developed out of the more economically efficient block holdings within a few generations. The most completely documented tract of land is the vast Jose Vasquez Borrego Grant made in 1750. It was later divided into the Dolores, Corralitos, and San Ygnacio Subdivisions. The first settlement was made at the Hacienda de Dolores on August 22, 1750. This settlement was abandoned, apparently during Indian troubles in the early 19th century. A settlement or Rancho of Dolores was founded nearby in the Dolores subdivision of the Borrego Grant by Cosme Martinez in 1859. Meanwhile, the town of San Ygnacio had been founded in the San Ygnacio subdivision in 1830. Until the early 20th century, an hacienda in the Corralitos subdivision was occupied by members of the Vidaurri family, who were descendants of the original grantee's daughter, Alejandra Vasquez Borrego de Vidaurri.
Also of interest are the Corridos, or ballads, composed by Mercurio Martinez and dealing with dramatic events in Zapata County history such as an escape from prison, a contested election and the destruction of Zapata by the rising waters of Falcon Reservoir.