When I start a new Sales Order, the main "Location" field is pre-populated. I can't find any workflow or script that sets this automatically... is there a setting or preference that would play a role in setting this?

There is a preference in Setup > Accounting > Accounting Preferences.

Thank you @Luis

@ericbirdsall the usual default I see is that it defaults to the Location of the Employee's record if that Order Management setting is blank.