Can't get Drush to function
I'm reporting back to provide my solution.

The site itself was Drupal v 7.51. As you can see, I was using Drush v. 8.1.5.

Reverting back to 7 corrected the issue and was done fairly easily following the modules unraveled tutorial here: https://modulesunraveled.com/blog/install-drush-7-and-8-and-automatically-switch-versions-based-project.

Regards