Here’s a link to some possible boats, but this is not nearly a complete list.  If you pack lightly you can get away with a solo boat, but a tandem boat can also be paddled solo if you need more capacity (and versatility as it allows you to bring along a friend).  However, my paddling buddies call solo tripping in a tandem “not ideal”.  The more ideal setup would be to have a solo canoe for soloing and a tandem for ummmm…tandeming

http://www.canoeing.com/canoes/river/

I agree with placid that the prospector model canoe is a good all-around tandem that can be solo’d.  I don’t go so far as to think it’s the end all canoe however.  If you are not planning on paddling any sort of rapids you can certainly get away with something that moves in a straight line more efficiently (the more rocker on the boat the better it turns, but the least efficient it goes straight).  The Mad River Explorer is a good comprimise boat, as is the Wenonah Aurora.  Bell makes some nice boats as well, but I’m not as familiar with their tandems. 

For solos, I really like the Bell Wildfire for river tripping and my Bell Traveller (pre-runner to the Bell Magic) is great for flatwater touring.  I don’t like the wenonah solo’s so much because they like to put those damn tractor seats in, which I hate.  I like the versatility to sit or kneel (or a combination of the two).

As for materials, they really have come a long way since the aluminum.  The royalex models can really take a beating and last a long time.  If you are more careful with your boat, and have more money to burn, kevlar and carbon fibre are super light weight, transmit power well as they are good and stiff, and can easily be portaged.  I have a fiberglass boat, a couple of royalex boats, and a kevlar solo boat.  They all work great, but of course the kevlar is easist to carry (something to certainly consider at an older age especially).  None of them transmit the cold and make all the racket that metal does.  Of course the advantage to aluminum is that you can leave them outsid and basically never worry about messing them up.  All others should be store inside or in the shade (always resting evenly on the gunwales).

The biggest suggestion I would make is to take advantage of instruction if it is available in your area.  We get people that have been paddling for years taking our Red Cross Canoeing classes and they are amazed at how much there is to learn in the way of proper technique.  Good habits of a vertical paddle, proper torso rotation, and only engaging the power to your knee (a bit further with a bent shaft) will translate into a more efficient stroke and less energy used.  If done correctly you really should be able to paddle all day and not feel exhausted at the end of it.

I’m not nearly as anal about waterproofing everything.  I have the absolutely must stay dry stuff, the “would be nice to stay dry stuff”, and the “hell it’ll dry eventually stuff”.  Most of the time I have my $2000 dollar camera setup sitting in my lap.  If the conditions make me nervous, I double dry bag it.

Ashland ..

Weight of your gear will depend a lot about how much money you can spend, how much security and comfort you want, how much food and what food you will take, how often you can purchase groceries and fuel for your stove, etc, the same as bicycle touring.  Weight is not nearly the factor in canoe tripping as bicycling, although it can mean bulk and extra trips on a portage .. but I prefer the extra trip or trips to not having comfort and security. 

Those dams will probably be a challenging portage, and you can check out my wheeled canoe cart/kitchen wannigan on my facebook .. Bob Mosurinjohn .. I find the cart helpful even on portages through the woods because portage trails are generally well packed down, and portages around dams on the Mississippi will almost certainly be on paved or packed roads, good places for wheels which I’ve used often and with no shame whatever as I’m not a ‘purist’ who shuns technology.

Even lakes (Flatwater) with no current can turn into whitewater through sudden winds .. the Ottawa River blew up from windless dead flat calm in 20 seconds with no warning at all just after I landed and tied my canoe; and the Mississippi will probably carry the same risk along with the risk of huge waves from commercial traffic, so I would stick with a canoe designed for touring and whitewater together, which the Prospector is.  A Prospector tracks (straight lines) as well as it rides rapids and whitecaps, and I can paddle my loaded Prospector three strokes without needing to make a yaw-correction stroke.  A canoe with a semi-V hull seems the best all around shape.  Avoid external keels as they hang up on rocks and logs, and can also make for an unstable platform for loading and unloading, getting in and out of the canoe, etc.  With the symmetrical Prospector you turn it end-for-end, paddling from what is normally the bow seat.  Again, unless you want to spend a lot of money unnecessarily by buying two or three different canoes for different purposes, I would buy a 17′ Prospector as light as you can afford, that way you can pick up passengers or a wife along the way.  Some ’touring’ boats are asymmetrical, which means they are more difficult to paddle solo unless you paddle on your knees because you can’t end-for-end them as the bow section is longer with a different shape than the stern section.   Please remember that I’m not promoting a certain manufacturer by recommending Prospectors, as most manufacturers make them.  Some folks will say I’m wrong about recommending a 17 footer as 16 footers are plenty of canoe, but I’ve used a 16 footer on all my trips, and it just wouldn’t do for two people with a good load.

I strongly recommend you learn your canoeing in the boat you make the trip with, because characteristics can vary greatly. 

And buy a yoke with your canoe .. you’ll never regret it.