A while back I wrote a program to calculate which cities are within 300 miles of the Mississppi River. I used a file called place2k.txt
from http://www.census.gov/geo/www/gazetteer/places2k.html . I only took 85 data points for the river, so the distances might have as much as 15 miles in error. I included all points within 315 miles of the river, just to be safe.