Way too slow for meteors
Definitely the correct speed, if not the correct vector, for Iridium. All my previous sightings have been north-to-south trajectories (but of course they have to return south-to-north somewhere in their orbits!). Definitely polar orbit, too -- too highly inclined for ISS or Hubble.
Too late at night for reflections off high-altitude aircraft ... also not long enough duration, and no accompanying sound.
Lat/long = 38.9110° N, 94.3820° W
I appreciate the help!