1. Take a map, a really good map. I took the DeLorme 3 miles to an inch road atlas, and it was vital. Directions to Lewis and Clark sites will send you off down obscure unpaved roads, and while those roads have names, Montana is chary of putting those names on road signs, and the map is the best way to find out where to go.
2. Nevertheless, don't be afraid to drive those unpaved roads. Montana keeps them in good condition. Only the occasional washboarding and the even rarer gully. But while the speed limit was typically 40 mph, 35 was about as fast as I could go without kicking too much gravel up. Once, far up in the mountains about a mile below the Continental Divide, I found a tree had fallen across the road. In my SUV, I was able to drive over the trunk, but I fancy that the sports car I passed going the other way a few miles later was in for an unpleasant surprise.
3. And when you get to your L&C site, even if it's far out in the wilderness, don't be surprised if there are interpretive signs, often well-researched and with very few factual errors. Comparing these with the info in my older guidebooks, it looks like the signage has been blooming in recent years.
(3a. OK, what errors were there? Two different signs said that Lewis left Sgt. Ordway in command of the portage camp at Great Falls when he set off to explore the Marias. No, Ordway and the canoe party hadn't arrived from upstream yet. Sgt. Gass was in charge pending Ordway's arrival. In the town of Salmon, Idaho, which dubs itself Sacagawea's birthplace (she was probably born somewhere in the area, but we don't know for sure), there's a sign claiming that her reunion with her brother, now the chief of their band, took place there as well. No, that happened over on the Montana side, at Camp Fortunate.)
4. And there's some very good museums. Best was the Forest Service's museum in Great Falls, of all things, whose extensive exhibit recounts the entire journey of the expedition, with emphasis on the native tribes they met, each referred to by both its common Anglo and own tribal name (though I'm not always confident in the accuracy of the latter). My favorite exhibit was the one where, if you press buttons for the language names in the right order, a recording of actors and a hypothesized script will reproduce the entire five-person translation process by which Lewis negotiated for horses with the Shoshone. The pathway winds creatively through the building, and when you get to the point where Lewis and Clark parted to take different routes on the return journey through Montana, the pathway briefly splits.
5. Also, the Sacajawea Center in Salmon, which is small but excellent. Gives a full account of her contributions to the expedition, which were useful, extensive, and honorable without having to make up any stories about her guiding the explorers across the continent, and, even more impressively, puts it in the context of modern Shoshone knowledge about their aboriginal customs and beliefs. So it forms a biography: first you see her as a Shoshone girl among her people, then as a captive of the Hidatsa, then heading off with these strange white men for a hoped-for reunion with her people. And what happened afterwards? The exhibit accepts the historically-likely story that she died in 1812, while noting the existence of a tradition that she lived to a great age in Wyoming, which is a fair way of putting it.
5a. This museum was still closed for the season, but unlike others that were closed had a notice on the website saying they'd open it by appointment. As I'd be on the road, I wasn't sure beforehand exactly when I could show up, but I phoned them and we worked something out, and someone was there to turn on the heat and let me in.
6. The other really good museum I visited was the Museum of the Rockies on the Montana State University campus in Bozeman. Nothing about Lewis and Clark, but a thunderously superb exhibit on the topic of dinosaur bones, Montana's leading geological product. Made an excellent update to my memories of long-ago college paleontology class.