Forging Their Legacy: Cooperation and Accommodation in the Lower Rio Grande Valley is an examination of the relationships created during the mid-nineteenth century between Anglo and Tejano elites in the five counties that make up the Lower Rio Grande Valley. Conducted through a quantitative lens, the five-chapter study seeks to demonstrate that, although the period between 1848 and 1870 was fraught with conflict and violence, the Anglo and Tejano elite of the Lower Rio Grande Valley came together in cooperation in order not only to survive these troubling times but to prosper. The thesis begins by identifying and analyzing the economic and political elite in the Lower Rio Grande Valley during the 1850s. A new crop of Anglo immigrants arrived with the Mexican-American War, but only a small number willing to assimilate to local Tejano culture were able to leave their mark on the Lower Valley. Chapter 4 relates the effect of the Civil War on the elite of the Lower Valley. It explores the profitable cotton trade during the war and the struggle that both Anglo and Tejano elites faced during Reconstruction. The thesis concludes with a macro-analysis of the twenty-two-year period from 1848-1870. It summarizes overall trends found in both the Anglo and Tejano elite communities and challenges the often-repeated argument of rapid dispossession by Anglos.