I love the idea of a GPS in 1700.
When was the first constellation launched? Somebody needs to think a little harder. Nice challenge though. I favor the mountain man equipment approach and the Corps of Discovery route. Harder to get lost that way, after all they didn't have a clue either. Being a lazy b*****d, I'd much rather follow (paddle) the water routes than walk the entire distance. Blast match, 'hawk & bowie, quality boots, compass, water bottle, cook pot, tarp, long bow & arrows, quality pack, fishing gear, multivitamins, small med kit, trade goods, and a "one over the world" blood chit style map. Most of the items have already been discussed in detail in the various survival threads. Oh - 18 months, Boston (or maybe New York) to Astoria. It shouldn't take that long but I'm lazy and the fishing might be decent enroute.
ETA: Forgot to include my G-shock - wouldn't want to lose track of the pick-up time.