You can find out who owns a building by gaining access to public records. Property is assessed by a city tax employee who will evaluate properties to assess what the property tax will be for the owner of the property. Every piece of real estate should have a record of who owns the property but you will have to do some leg work if the information in not readily available on the towns website
You should first call the town hall in the city the building is located. The town hall should have a list of property that has been assessed for property taxes. If for some reason the town hall does not have this information ask where it is, it should be readily available since it is public information
Call the county office where the property is located and let them know you would like to look at a deed on a property. Once a property has been sold the deed is recorded by the county clerk. There may be a nominal fee for them to pull the deed.
Ask county and town officials questions. They are there to help and that is their job to give information about records or any other information that is available to the public.
Search Online. This will be hit or miss. First search you cities town hall and type in tax assessments in the city search bar. If you city does not have this option you can do the same thing with the county's website. Type in "recorded deeds" and they may have the information you are looking in electronic format.
You can hire and outside party to do the research. If you are on a time crunch, live in another state, or just do not feel like doing the leg work there are Internet companies that will do the research for you, but the price will be a bit high, usually around £32-$100.