Answer

1. Add one level of the hierarchy (for example, states) to the view by double-clicking the field in the Dimension pane. This will add the generated Latitude and Longitude fields to the Column and Rows shelf.
2. Add an additional instance of Latitude (generated) to the Rows shelf.
3. Add the other desired level of the hierarchy (for example, city) to the Marks card for the second Latitude (generated) field.
4. On the Rows shelf, right-click on the second Latitude (generated) field and select Dual Axis.

Additional information

Custom Latitude and Longitude fields (typically existent in the underlying data) cannot be combined with the Tableau Desktop-generated Latitude (generated) and Longitude (generated) fields, but can be combined with existing geographic roles. For example: To map addresses on top of ZIP Code, add Latitude and Longitude (database fields, not Generated) to Column and Rows, then specify the level of detail by adding Address to the Detail shelf.  Add a second iteration of Latitude to the Rows Shelf, then replace Address with ZIP Code on the second iteration of Latitude on the Marks card, then perform step 4 above.  

Note: Doing so will only map ZIP Codes that match up with the Addresses present in the underlying data.