Who was a famous steamboat captain who became a popular author about the Mississippi River region in the 1800s?

Samuel Clemens'

Explanation:

Life on the Mississippi was the book that launched the now well known Samuel Clemens' career as a "serious" author. Clemens, more well known by the title Mark Twain, paints Mississippi steamboat living and the workings of the river itself as a tribute to that great river.

Mark Twain