The 1854 Gazetteer of the United States by Thomas Baldwin shows:

DUVAL, a county in the north-east part of Florida, bordering on the Atlantic, has an area of 430 square miles. St. John's river flows along the eastern border until it enters the sea, and Nassau river forms its north boundary. The surface has but little elevation: sugar, cotton, Indian corn, and sweet potatoes are the staples. In 1850 this county produced 391 hogsheads of sugar; 216 bales of cotton; 51,788 bushels of corn, and 27,674 of sweet potatoes. It contained 5 saw mills, 8 churches; and 64 pupils attending public schools. Capital, Jacksonville. Population, 4539, of whom 2433 were free, and 2106, slaves.