Spanish and French missionaries carried endemic diseases: resulting in epidemics of smallpox, measles malaria, and influenza among the Caddo.

[7] The majority of the settlers had migrated from other southern states and brought enslaved African Americans with them as workers, or purchased them in slave markets.

The county was developed as cotton plantations, and enslaved African Americans made up 51 percent of the population in 1860.

[8] In February 1869 the river steamboat Mittie Stephens caught fire from a torch basket that ignited a hay stack on board.

On October 4, 1869, George Washington Smith, a delegate to the state Constitutional Convention, was murdered by a band of vigilantes while incarcerated in Jefferson.

Various forms of the white primary survived until 1944 when a US Supreme Court ruling overturned the practice as racially discriminatory and unconstitutional.

[12][13] The Marion County brick courthouse was erected in 1914, designed by architect Elmer George Withers.

[14] In the early 20th century, the Dick Taylor Camp of Confederate veterans erected a monument to honor the county's dead in the American Civil War, placing it outside the courthouse.

From 1933 to 1937, during the Great Depression, men were hired into the Civilian Conservation Corps and made improvements to the park.