When Sheriff Truman, Hawk, and Ed meet Cooper at the Double R and tell him about the Bookhouse Boys - "the evil in these woods" Truman quote would lend itself to awareness of the Lodges so why don't the Bookhouse Boys help out more or have records from past Bookhouse Boys about Lodge activities in Twin Peaks?

It also seems like Cooper would ask for further help from Hawk for further Lodge knowledge or possibly any other Native Americans he knows in the area that may have info about the Lodges.

I know Major Briggs is in the military and everything is classified, but it seemed like towards the end he started giving out more and more knowledge of the Lodges because it became more personal and especially with Sarah Palmer delivering a message from the Lodge itself in the finale.

Do you think the Bookhouse Boys, local Native Americans, or the military would have played a major role in the future Lodge investigations in Twin Peaks?  Or do you think Cooper and the local authorities already did this during the series and had no such luck?

It just seems like all of these leads would be natural progressions for the investigating characters.

I'd say that both the army and the Bookhouse Boys don't really know much about the Lodges...at least not in detail. The army was still looking for the White Lodge and how they treated Briggs shows that it was their first "contact". As for the Boys, I've always considered they're not what they used to be, they are in complete decadence... A secret society dedicated to fighting an ancient evil and now what do they do? Going after people like Bernard Renault, going undercover in drug operations, etc. They know the folklore ("goes way back"), they know it's there, but they haven't witnessed anything, don't know about inhabiting spirits, rings, etc. (look at Truman's and Hawk's reaction after BOB reveals himself in Leland) and certainly don't know how to fight it; maybe the old Bookhouse Boys did, but they don't.

Summarizing, they wouldn't help much in the investigation...

I think they could try to interview local Native Americans and ask if they knew anything especially concerning the Owl Cave.  They could learn more from their legends concerning the Lodges and possible recent incidents or when they were younger exploring in the woods around town.