During the 14th Boule held in New York, New York December 27-30, 1939, the Grand Chapter voted to establish the Southwestern Region of the sorority. Over the course of the subsequent months, the strategy for the region's organization was developed under the leadership of Soror Mary Scales Greenwood of the Gamma Sigma Chapter of Houston, Texas. Soror Greenwood became the First Syntaktes of the Southwestern Region and during her tenure as Syntaktes (1940-1948), most of the region's chapters were organized.

Although the Southwestern Region was officially established in 1940, there was a strong presence in the southern part of the country dating back to 1928. Six educators interested in furthering the sorority's mission organized and established the Alpha Lambda Chapter at Texas Southern University and Gamma Sigma Alumnae Chapters of Houston, Texas in 1928. Alpha Lambda and Gamma Sigma also hosted the first Boule held in the Southwestern Region December 27-29, 1938 in Houston.

Since its establishment, the region has contributed to the Sorority's legacy and from its delegation key components for the organization have been birthed. One of the most noted contributions from the region is the designation of "The Poodle" as the Sorority's official mascot by Quindonell Robertson, 8th Syntaktes of the Southwestern Region.

It was also through the Southwestern Region, that another avenue for women in the community to serve was created. The Philo Affiliate was organized in 1943 in Galveston, Texas and since inception has become one of two internationally recognized affiliate organizations of the Sorority. Through the Philo Affiliate, women who are not affiliated with Greek-lettered organizations, can provide meaningful contributions to the communities where Sigma Gamma Rho alumnae chapters are located and serve. Members of the Philo Affiliate also engage with the organization on national, regional and local levels serving in leadership roles and assisting with the growth of this great sisterhood.

The Region is now comprised of nearly 100 alumnae and undergraduate chapters and continues to provide meaningful service to the four states of its jurisdiction - Arkansas, Louisiana, Oklahoma, and Texas. The Southwestern Region consistently executes the Sorority's essential programs, increases awareness of the organization and its purpose, promotes its national partnership and initiatives, and ensures the Sorority is at the forefront of all issues impacting its service area.