I always think Fort Nisqually is the best choice, but then, I may be biased.
Incidentally, our first event of the season, Sewing to Sowing
, is this Saturday the 23rd. The volunteer application
is here (14-year-olds will need to have a parent on-site, though they don't necessarily have to dress up as well); there's also a teen program which runs January-December, so we have a group of nice volunteers around your age. If you decide to join us, the sewing guild will be happy to help with fitting and construction techniques, and there's also a lending wardrobe for volunteers, so you don't have to get all your own things made at once.
may also be an option, if your interests tend towards Civil War, though I don't recall which groups are currently active in the SE; my unit meets out of Lakewood, but the events are all over the state (Yakima, Spokane, Snoqualmie this summer, though there's usually a reenactment at Chehalis, too). There are also a few historic homes (particularly around Olympia) which have small living history programs; further south, Fort Vancouver
does living history spanning the 1830s to 1930s, and the NCWC
has Civil War events in Oregon.
As Paula said, you can do a corset with one layer of material, the boning held in with tapes, or with two layers of material and the boning sandwiched between them. In either case, you want a tightly-woven all-cotton fabric--something that doesn't stretch. For double-layer corsets, I usually do both layers of the same material (I've used both sateen and twill), though I love the lightness of my single-layer coutil corset.
I haven't personally made up the Dore, but usually spiral steels are placed along curved seams or other places which take advantage of their ability to bend (see here
for just how much spirals can bend); depending on your figure and how you lay the steels, it may be possible to do the entire corset with straight steels, or you may wish to use both types. As I understand it, whalebone/baleen can curve around non-straight seams, so the spiral steels are a slightly-post-period alternative to a no-longer-feasible period material. Artificial whalebone and rows of cording are also options for such areas.