"John" wrote:

Thanks, Ron, but that doesn't answer my question.
I tried the frequencies on the chart and they didn't work.
Once I climbed up to 4000', I got 'em on one of the frequencies I
mentioned, but I can't remember which one.

Where do we find the working frequencies for ATC?
If there are any limitations to the frequencies given, that should be
posted, too.

John, your question actually was answered by Ron and also by Elliott.

Examining your chart in the vicinity of Brooke VOR (BRV), the two closest
airports are Stafford (RMN) and Shannon (EZF). When you look up either of
those airports in the A/FD, you'll find that they are serviced by Quantico
Approach on 127.05.

This is a very common and useful strategy for locating "obscure" frequencies
that don't appear on a sectional with big blue or magenta boxes around them.
Just find the closest airport to your position and refer to the A/FD for the
controlling approach facility. If the airport has an IAP and you've got the
plate handy, that works too.