By some counts there are 97 (now 95 as Diamond Peak Patrol Tower burned down and Aeneas has been removed) of the 680 plus sites that still have a structure on them. Peakbagger still has 93 which includes the burned down one and does not include the newer ones. These are the Standing Lookouts Of Washington (SLOW). Of these some of them are still staffed and in use for their original purpose. Some are open to the public and maintained by various volunteer groups and some are even available to rent!
You can rent a lookout for a night's stay or more than a night if you choose. If you go to tag one of these, remember the people in it paid to have the place to themselves and do not disturb them unless they invite you in. Click through to get more details how to rent.
These are not for rent. You can stay the night if there is room. Some of these kind of turn into a party with people arriving at all hours. There is usually a group that is maintaining each of them and there is an opportunity to volunteer. Click through for more details. Coming soon: a sign up sheet for a work party at a lookout or other ways to contribute to maintaining these structures.
These lookouts are being used for there original purpose. If you find anyone there, they are working and you need to respect that. Many times they are lonely enough to enjoy a conversation, but use your judgement and ask if it is OK to visit and look around.