I am trying to split a money market muni income between one state and all other states. Turbo Tax won't let me enter "All Other States." Do I have to list every state?

No. You only have to list the states where you are filing an income tax return. Use Multiple States for municipal income received from securities of other states.

1. Type dividends in Search (magnifying glass) in the top right
2. Click Jump to dividends
3. On “Your investments and savings” Edit your dividends
4. On Now, let’s review your 1099-DIV check your Box 12 amount, then Continue
5. On "Do these uncommon situations apply?" select None of these apply, then Continue
6. On "Do these uncommon situations apply?" select None of these apply, then Continue
7. On “Tell us more about your exempt-interest dividends," tap I earned exempt-interest dividends in more than one state
8. Select Your State and Multiple States and enter the amount of other state dividends in Multiple States

.......and the "Multiple States" selection is at the very end of the list of states.