I have a leased line that is 6.5 miles (about 10.5 km). I have been told that it is a continuous copper connection. What options do I have regarding networking over this line and what kind of equipment would I need?
I assume that you mean "Leased telephone line" and that it is "twisted pair". You are going to have loss in the line due to the capacitance and inductance, which means you will have limited bandwidth, and thus data transfer rate might be limited. Much depends on the size of the cable. The cable MUST be terminated with its characteristic impedance at both ends, otherwise you will have plenty of echoes running up and down the line, which would disrupt communications.
Since this is "leased" line, I would talk to the phone company (or whomever the line is leased from) to find out what the possibilities are.