I found that GNU screen does exactly what I want (just type
screen in terminal), but only after I spent a few minutes learning some basics. Here is the jump start I needed on key bindings (straight from the man page) - note that you need to install the GNU version for vertical splits (listed after the FAU version that was in my Mavericks).
Screen version 4.00.03 (FAU) 23-Oct-06
(included in Mavericks and likely similar in earlier)
The following table shows the default key bindings:
C-a ' (select) Prompt for a window name or number to switch to.
C-a " (windowlist -b)
Present a list of all windows for selection.
C-a 0 (select 0)
C-a 9 (select 9)
C-a - (select -) Switch to window number 0 - 9, or to the blank window.
C-a tab (focus) Switch the input focus to the next region. See also split, remove, only.
C-a C-a (other) Toggle to the window displayed previously. Note that this binding defaults
to the command character typed twice, unless overridden. For instance, if
you use the option "-e]x", this command becomes "]]".
C-a S (split) Split the current region into two new ones.
C-a ? (help) Show key bindings.
C-a \ (quit) Kill all windows and terminate screen.
C-a * (displays) Show a listing of all currently attached displays.
Additional items with 'Screen version 4.02.01 (GNU) 28-Apr-14'
sudo port install screen just now)
All of the items listed above in the 4.00.02 (FAU) version, as well as:
C-a S (split) Split the current region horizontally into two new ones. See also only,
Same above, but this clarifies that it is horizontal.
C-a | (split -v) Split the current region vertically into two new ones.
Note: I tried searching the web for this, but words such as 'screen', 'terminal', and 'split' are so common as to make the man pages easier for me.