Let me respond to your first question Maggie. There is no real search yet for looking for categories. There is an overall list of categories you can look at that is really long. Probably the simplest way to see if a location already exists is to do the following.
1. Go to http://www.wikitree.com/wiki/Category:United_States_of_America
2. Navigate to state
3. Navigate to County
4. Look for your location under the county heading, generally there will not be a further "drill down" beyond county.
If there is no location then yes you can create it. The simplest way to do it is probably as follows.
1. Enter an edit session on the profile you are interested in adding the category to.
2. In the body of the profile window you will enter the following (Note for some reason to get the category to work properly it should be placed above the ==Biography== line in the profile window): [[Category:CITY, STATE]]. For instance to create a category for Titusville, Pennsylvania you would type [[Category:Titusville, Pennsylvania]] - this is also how you would add an existing category to a profile. The only exception to this is if in the same state more than one location has the same name, for instance there is a Troy Township in a least two different counties in Pennsylvania so in that instance the preferred format is [[Category:City, COUNTY, STATE]] or using our example [[Category:Troy Township, Crawford County, Pennsylvania]].
3. Save your profile and navigate to the profile page. If the category does not exist the location will be in red under the category section or it will be in black if the category does exist .
4. If the location is red click on it. This will take you to the category you just created for this location. Now you just need to link it to something.
5. Click on "edit" on the right side of the page. Then in the text box type [[Category:COUNTY, STATE]] for our Titusville example [[Category:Crawford County, Pennsylvania]]
6. Hit save at the bottom and you should be done as all the other links from county are completed.
When you navigate back to you profile the location under the categories section should now be black.
If you have questions or problems please let me know and I will be happy to help. [[Chelton-4]]