Mercedes was officially founded on September 15, 1907, to serve as the headquarters of the American Rio Grande Land & Irrigation Company. It serves well as a case study to showcase the great change in the culture and economics of the Rio Grande Valley that occurred in the early 1900s. Mercedes was not founded in a vacuum, however, as many early Valley histories of the region tended to portray. My presentation examines all the socio-cultural factors that led to its founding, and the historical context surrounding this event. Because this is presented to a genealogical group, the presentation will focus on how historical events impact our personal family histories. The European, as well as Native-American roots of the people of the Rio Grande Valley, will be discussed to provide a deeper understanding of what is pertinent in personal genealogy studies.