You can find an unknown road or street numbers for abandoned or vacant property by consulting the proper authorities. Civil offices use numbers for roads as well as a names.
Contact the local postal office to find the number of a property or vacant lot.The post office may ask for a description and landmarks near the location.
Consult a map. Since federal routes, highways and interstates are typically referred to by their number rather than a name, you can determine the road's number by consulting a map or an atlas.
Contact your state's Department of Transportation. To determine a secondary road's number you need to know the county the road is in and the road's actual name. Most departments of transportation have this information available via an online database.