OK If you follow the pennsylvania link you get to Regional/North_America/United_States/Pennsylvania/Transportation/Taxis/
You want the equivalent Nebraska category which does not exist as there are no/not enough taxi sites. So if your site was eligible you would suggest it to Regional/North_America/United_States/Nebraska/Transportation/ (and if you look at
http://www.dmoz.org/Regional/North_America/United_States/Transportation/By_State/ you will see it has Nebraska@ ).
BUT where you suggest your site is not the area in which you work but the town in which you have your office or home base. To be eligible for the state category, you would have to have offices in more than one county of the state.
By definition taxi's will travel all over the place and are quite prepared to go anywhere that a customer wants them too as long as they can pay. Here in the UK, they will go to France, Belgium, the Netherlands and even Germany for the day if required - they still only get listed in their home town.
So if you have one office or homebase, the town that it is in is where you suggest your site.
To get your coverage (i.e. how far you are prepared to go for pickups/dropoffs etc) you say that on your website and then can put it in your description (e.g. 'Taxi service covering A,B, C and D counties' ).
regards