The driving distance from Gulfport, Mississippi to Jackson, Mississippi is 158 miles via US-49 N per MapQuest. The driving time per MapQuest is 2 hours and 49 minutes.
You didn't pick a particular spot in Mississippi, so I picked Gulfport for this question.
About 75 miles by road.
about 189 miles, maybe 186 if you cut corners
63 miles
98 miles
New Orleans is about 90 miles from the mouth of the Mississippi River.
about 200 miles
New Orleans stands on the Mississippi river.
About 856 miles.
It is 207 miles according to Google Maps.
Google Maps estimates the driving time as 3 hours and 14 minutes.
It was the use of the Mississippi River and the Port of New Orleans
The driving distance from Saint Louis, Missouri to Jackson, Mississippi is 490 miles via I-55 S per MapQuest. The driving time per MapQuest is 7 hours and 14 minutes.
The driving distance is 80.1 miles.
The driving distance is 638 miles.
Mississippi
New Orleans source: http://www.eosnap.com/?tag=mississippi-river