The NALMA system carves up the last 65 million years (or so) of geologic history based on characteristic mammals that roamed the continent during discrete intervals. Just as a classic car buff can pick out a ’57 model from a’58 based on the shape of the headlights, or an art historian can determine when a landscape was painted from the collars on the figures in the background, a paleontologist can stumble across a fossil Bison tooth and know that she’s walking in Rancholabrean sediments. Bison, those icons of the American West didn’t wander into North America from their ancestral Asian homeland until about 300,000 years ago (or so). Likewise, various extinct rhinos, horses and weirder beasts yet serve as indices for particular intervals, intervals that usually take their name from a nearby town or river.
The map at top shows a rough itinerary scattered across 12 states. If I tried to do the trip in chronological order, which would be stupid, and nonstop (even more stupid) the trip would take about 6 days and 6 hours and cover 7,755 miles (12,480 km). The path would retrace substantial portions of the Oregon Trail, the Transcontinental Railroad and Route 66. I would visit Native American reservations, derelict garrisons, an enormous metropolis and several places so small they aren’t even recognized as Census Designated Places. I would pass through towns featured in Steven King novels and the site of a major uranium spill.
As shown in the photos above, the magic of Creative Commons search and Google Maps makes actually making the trip almost a superfluous gesture.
Would be fun though.