You may be able to find the builder from the tax records. Check out http://www.wadtx.com/ and put in the address. Sometimes you can see sometimes you can't. If you can find the builder you can contact them for plans. They may provide them, they may not, they may want to charge you for them. You might check with the building inspector to see if they have plans, but I doubt it.

Your city planning commission may be able to help you - or at least point you in the right direction.

A Realtor can pull tax information on a property and find the history, including last sales transaction. Are you asking how to find a floorplan? If the property was built within the last few years, a Realtor may have a copy of the floor plan from the builder, or the homeowner might. Floor plans are not stored in any county records. Who built a property might be found in the town records on permits.