Capital gain tax on gifted property, which was inherited by uncle from grand father

This discussion addresses the complexities of calculating capital gains tax when a property is inherited through multiple generations. The user's sister is selling a house inherited from their uncle, who originally received it from their grandfather. Since the original purchase price is unknown, advice is sought on determining the capital gain, with a suggestion to obtain a valuation report for the property's fair market value as of April 1, 2001.