Assign unknown locations by clicking the unknown indicator in the lower right of a geographic visualization, as shown here:

This will give you the following options:

• Edit Locations
• Filter out unknown locations
• Plot at the default location (Latitude and Longitude of 0, a location that is sometimes humorously referred to as Null Island, located just off the west coast of Africa).

The indicator in the preceding screenshot shows 336 unknown locations. Clicking the indicator and selecting the Edit Locations option allows you to correct unmatched locations by selecting a known location or entering your own Latitude and Longitude information, as shown here:

The first three options allow you to specify the geographic context by which Tableau determines the location of a field value. You may specify a Country, State, and/or County.

For example, Tableau may not recognize the city Mansfield until you specify the State (in the United States alone there is a Mansfield, Texas; Mansfield, Ohio; Mansfield, Kansas; and about a dozen more!) In this example, you may specifically select a constant State or let Tableau know which field in the dataset defines State.

You may also set individual locations by clicking the Unrecognized label in the table and matching to a known location, or by entering a specific Latitude and Longitude.