Thanks to all who helped with this.  I finally found the answer.

In my .emacs file, I had 2 lines:

(autoload 'c++-mode "cc-mode" "C++ Editing Mode" t)
(autoload 'c-mode   "cc-mode" "C Editing Mode" t)

However, near as I can tell, these did not actually load anything until a
file matching the mode criteria was visited.  Any lines referencing any
variables
defined by those modes were not defined in emacs' scope until a file of the
mode type was visited.  By then it's too late to affect any of the
variables.  By changing
the lines to:

(load "cplus-md.elc")
(load "c-mode.elc")

The variables (especially c-auto-newline...thanks G Anna!) are now defined
and can be manipulated; in my case, to turn off the auto-indentation
feature:

(setq c-auto-newline nil)

This gets me what I need, but is it wasteful?