In 1924, Adelaida Cuellar and her children took a break from farming in the fields to open a booth at the Kaufman County Fair. The booth served tamales, enchiladas, and chili and brought in $300 in profit-more than the family usually made in a year from farming. From these humble beginnings, the Cuellar children would go on to open and operate a multi-million dollar business founded on the recipes and work ethic of their parents.

After running restaurants separately in Texas, Oklahoma, and Louisiana, the Cuellar brothers decided to pool their resources in 1940 to open and operate a restaurant venture in Dallas. The restaurant, located at 3514 Oak Lawn, opened under the name El Chico and was an instant success with two more restaurants soon following in Dallas and Ft. Worth. By 1978, the El Chico Corporation run by the Cuellar brothers had opened 95 restaurants in 11 states and was bringing in $50 million a year.

The Frank Cuellar Sr. Collection contains hundreds of photographs and scrapbook pages of the Cuellar family as well as newspaper clippings and other printed materials documenting the family and business activities of Frank Cuellar Sr. and his family.