During the Civil War, McIlhenny fled with his in-laws, the Avery family, to Texas, where he served as a civilian employee of the Confederate army, first as a clerk in a commissary office, then as a financial agent for the paymaster.

The South's economic collapse after its defeat ruined McIlhenny, who now lived with his in-laws in their plantation house on Avery Island, Louisiana.

[4] In 1870, McIlhenny obtained letters patent for the sauce, which he packaged in cork-top two-ounce bottles with diamond logo labels very similar in appearance to those in present-day use.

[9] At first McIlhenny sold the product mainly along the Gulf Coast in places including New Orleans, New Iberia, Louisiana, and Galveston, Texas.

By the early 1870s, however, he had broken into larger markets, such as New York City, Philadelphia, and Boston, helped by major nineteenth century food manufacturer and distributor E. C. Hazard and Company.