Consider getting across America in a car. There are numerous ways to go! You can head across the northern states, the southern states, slice across the middle, or just roll your own route as the mood strikes you. With America's interconnecting freeway structure you're never really far from gasoline and a town with a warm meal and a comfortable bed. Even if you get detoured by a hundred miles you can comfortably make that up in less than an afternoon.
This kind of total open road freedom sadly isn't the same on a bike. While, yes, any of the roads available to a car are open to bike - there are a lot of reasons to very carefully consider your route before setting out. If you've ever been on a road trip you may frequently notice indicators that the next rest stop (not a town with all the amenities) is in thirty miles. That's thirty miles without being able to fill up a water bottle, and in the heat of summer that can be a long time.
Also, if you've ever ridden a bike in heavy traffic you've likely experienced that cars don't always see bikes or that some roads simply aren't very safe to ride on a bike. This can stem from a lack of a bike lane, a poor shoulder, a generally narrow road placing you uncomfortably close to cars, or simply not knowing where you need to go and being nervous about being in an unknown town. Combined with the fact that a forty mile mile detour could cost you almost an entire day of riding - it's extremely important to carefully plan your route.
So, while I like adventure as much as the next guy, I'm not quite adventurous enough to set out on a 5,000 mile journey without a map designed for a cyclist. Luckily, however, a company called Adventure Cycling exists and have spent the last thirty years building out safe and well documented maps for cyclists to travel all over the United Sates!
Adventure Cycling pioneered the "TransAmerican Trail" (shown at left, image copyright Adventure Cycling) which is a 4,200 mile route from Astoria, Oregon to Yorktown, Virginia. This route has continually been revised and tweaked over the years to include the safest roads and highlight all of the landmarks a cyclist could ever need along the way. From diners, to campsites, to beds and breakfasts, to bike shops - it's all there.
I recently purchased a set of maps for the TransAmerican Trail and I'm really pleased with how they're laid out. They're broken down into short segments with well marked labels for local attractions with both a graphical map and a turn by turn breakdown with mileage markers. The map itself is designed to fit into a handlebar map bag (which allows a cyclist an easy view of their map) so you can quickly see where you're going along the way.
Now, because I'm a bit of a nerd, of particular interest to me is that Adventure Cycling has recently begun to release KML / GPX files (which are a GPS standard that GPS devices can read as a route sheet) for their TransAmerican Trail on the Adventure Cycling website. This means that, assuming I can find a suitably priced GPS unit, I'll be able to get turn by turn directions from one end of the country to the other. And, not only that, all the cycling specific landmarks will be dialed into the device. Not too bad!
So, this is how I plan to find my way across: by the path followed by thousands of other cyclists before me over the last thirty years. Armed with a map, a GPS unit, and my trusty iPhone I don't foresee myself getting TOO lost on the journey.