The Mississippi River is known as the Middle Mississippi from the Upper Mississippi River's confluence with the Missouri River at St. Louis, Missouri, for 190 miles (310 km) to its confluence with the Ohio River at Cairo, Illinois. The Middle Mississippi is relatively free-flowing.
As Hopper notes, eight major U.S. airlines offer free cancellation for tickets purchased at least seven days in advance: Delta, United, US Airways, JetBlue, Southwest, Spirit, Frontier and American (in American 's case, you'll hold your ticket instead of purchasing it).
It should be very easy to cancel a RESERVATION before departure. You can either call the airline or your travel agent (if you used one). All they do is cancel all the flight segments in your itinerary. There is nothing else to it. Your ticket is still good one year from date of issue. (No need for confirmation number.