n 1875, the Dallas Herald published an article by a former Fort Worth lawyer, Robert E. Cowart, who wrote that the decimation of Fort Worth's population, caused by the economic disaster and hard winter of 1873 which dealt a severe blow to the cattle industry, combined with the railroad stopping the laying of track 30 miles outside of Fort Worth had caused Fort Worth to become such a drowsy place that he saw a panther asleep in the street by the courthouse. The nickname Panther City was enthusiastically embraced when in 1876 Fort Worth recovered economically and many businesses and organizations were named Panther.
 

Read the historical article that started it all...

February 2, 1875 Dallas Times Herald Article
FORT WORTH IN A COLD SWEAT. Mass Meeting of Citizens--A ''Panter'' Loose In Her Streets.

From the "History of Texas, Fort Worth and the Texas Northwest Edition", Volume II, 1922...

THE PANTHER CITY

At this place it may be well to answer the inquiry so often propounded "why is Fort Worth called `Pantherville' or `Panther City'?'

Among those who left the place when the cyclone hit it was a young lawyer who had come hither from Georgia, one Robert E. Cowart. He went to Dallas, where he still lives, and is one of the promoters of the scheme to get deep water in the Trinity at that place. Cowart was, and is, a bright man. He has a keen sense of the ridiculous and verbiage that can make an Indian's hair curl. He lived long enough in Fort Worth to become acquainted with the peculiarities of its people. It was he who furnished the story that gave Fort Worth the name of the "Panther City." Knowing the conditions that prevailed here, he wrote a communication for the Dallas Herald, then the leading paper of North Texas, telling of the discovering of a panther in the streets of Fort Worth, and the action taken by the people.

No attempt was made to deny or explain the charge. It was accepted as a fact. The town was by common consent christened "Pantherville." Every one named every thing "Panther." There were "panther" stores, "panther" meat markets, "panther" saloons. The "Democrat," a weekly paper being printed here secured a cut of a panther couchant, which it displayed at the head of the paper. A fire company organized at about that time named the engine the "Panther." Two panther cubs were advertised for and secured by the local paper and they were housed in a handsome cage at the firehall. When, a little later, Dallas gave a big celebration or demonstration of some kind the wagon with the panthers were taken over there, drawn by four white horses and escorted by forty good and patriotic citizens of the town clad in white uniforms. It was easily the most attractive part of the procession on that occasion. Fort Worth is still known as "Pantherville," or the "Panther City."