Where are original real estate abstracts filed?
There is no one answer to this question.
Real Estate Abstracts or more correctly stated, " Abstracts of Title" are a compilation, usually by a third party, of the history of / and the status of title to a specific parcel of land. These manuscripts are a detail of all the transfers, and encumbrances associated with a specific parcel of land over a period of time. Also, pending on which state you are in, there may not be abstracts on property any more.
First, let's assume that you live in a state that has abstracts and you need to find one relating to a specific piece of property. Here a list of places to check first.
Attorneys or title office that completed the closing on behalf of the buyer or seller.
Title / abstract company if known who completed that last update of the abstract.
County Clerk or recorder's office of the district that stores deeds and mortgages for your area.
Current or Previous owner of the property in question.
If you do not know any of the information above, then a suggestion would be to go to the clerk /recorders' office and look for the most recent vesting deed or mortgage filed. Typically the deed, mortgage, deed of trust will be notarized or have an insignia of an attorney of title company that performed the closing on behalf of the property owner. This may provide a starting point for your search to obtain the most recent update of the abstract.
Your question mentioned "original real estate abstracts". If you are looking to obtain historical information, the best place to start would be the County Clerk's office or the recorder's office. Many times this office completed the abstracts on the parcels from the mind 1800's through the mid 1900's when abstract and title companies took over for the local counties.