 In 1839 the City of Galveston adopted a charter and was incorporated by the Congress of the Republic of Texas . The city was by then a burgeoning port of entry and attracted many new residents in the 1840s and later among the flood of German immigrants to Texas , including Jewish merchants . Together with ethnic Mexican residents , these groups tended to oppose slavery , support the Union during the Civil War , and join the Republican Party after the war . 
