Viperdoc wrote:

They are generally considered confidential, although you may obtain the
information under the freedom of information act.

They aren't confidential. If they were I would know, some documents and
information is and we are told that. These aren't. It's not really
useful information if I gave you a map of the various boundaries.
Individual sectors within centers and approach controls are combined and
decombined at regular and irregular intervals. Plus any two controllers
can get together and agree to do just about anything for a given amount
of time, thus making any published boundaries irrelavant. We do that
virtually every night with Salt Lake center. The call goes like this,
from the ZLC controller to the BIL approach controller....."Down to 9
til 5?" I answer..."Yep." Thus circumventing months and months of
careful planning and negotiating between untold numbers of high level
management and their staffs. Our letter of agreement states that all
IFR aircraft will be at or descending to 13,000. That's too
constricting so center wants approval to go down to 9,000 and they don't
want to call for each one and I certainly don't want to have to answer a
call for each request. So I could show you many maps of carefully drawn
boundaries but they are almost never used in that manner.