Kyler Laird writes:

Anyone know where to get the boundaries for sectionals? (I want to be
able to determine which sectionals contain a given point.)

This question showed how naive I was. Sectionals don't have well-
defined boundaries. Most have a well-defined SW corner of latitude and
longitude (on the South side) and extend to the North and East from that,
but several extend vertically to some horizontal (to the image, not a
line of latitude) line. Then there's Jacksonville with its insets.

Regardless, the SW corner is a good place to start for this. Here's my
list. Corrections will be appreciated.
Albuquerque|-109.0 32.0|
Atlanta|-88.0 32.0|
Billings|-109.0 44.5|extends vertically
Brownsville|-103.0 24.0|
Charlotte|-82.0 32.0|
Cheyenne|-109.0 40.0|
Chicago|-93.0 40.0|
Cincinnati|-85.0 36.0|
Dallas-Ft Worth|-102.0 32.0|
Denver|-111.0 35.8|cut horizontally
Detroit|-85.0 40.0|
El Paso|-109.0 28.0|
Great Falls|-117.0 44.5|cut horizontally
Green Bay|-93.0 44.0|
Halifax|-69.0 44.0|
Houston|-97.0 28.0|
Jacksonville|-85.0 28.0|insets
Kansas City|-97.0 36.0|
Klamath Falls|-125.0 40.0|
Lake Huron|-85.0 44.0|
Las Vegas|-118.0 35.8|cut horizontally
Los Angeles|-120.0 32.0|extends to left
Memphis|-95.0 32.0|
Miami|-83.0 24.0|
Montreal|-77.0 44.0|
New Orleans|-91.0 28.0|
New York|-77.0 40.0|
Omaha|-101.0 40.0|
Phoenix|-116.0 31.25|cut horizontally
Salt Lake City|-117.0 40.0|
San Antonio|-103.0 28.0|
San Francisco|-125.0 36.0|
Seattle|-125.0 44.5|cut horizontally
St Louis|-91.0 36.0|
Twin Cities|-101.0 44.5|cut horizontally
Washington|-79.0 36.0|
Wichita|-104.0 36.0|

--kyler