 In 1783, José Antonio de Evia, a Spanish navigator, surveyed the area and named the bay Galveston to honor Bernardo de Gálvez, who supported the United States in the Revolutionary War.Galveston County was formally established under the Republic of Texas on May 15, 1838.The county was formed from territory taken from Harrisburg, Liberty, and Brazoria Counties, with governmental organization taking place in 1839.