Drop down list opens another list based on first selection

I am trying to figure out the easiet way to do the following.... 

I need a drop down list that has every county in my state. Once someone selects the county in the first drop down list, a new list should appear that lists the court locations in that county.

For example:

List 1 will show the following:

County 1

County 2

County 3

once a county is selected, a new list appears that shows,

Court Location 1

Court Location 2

Court Location 3

Court Location 4

Alternatively, I could put all infomation in one list, but I can't have the county information to be visible when selected. 

fo example, the List would show:

County 1  - Court Location 1

County 1  - Court Location 2

County 1  - Court Location 3

County 1  - Court Location 4

but when you select "County 1 - Court Location 3", only Court Location 3 will appear on the document.