Complex sentence: The Jefferson Davis Presidential Library was established at Beauvoir Plantation, the white-columned Biloxi mansion that was Davis's final home, in 1998, after its use for some years as a Confederate Veterans Home.
Split into simpler sentences: The Jefferson Davis Presidential Library was established at Beauvoir Plantation in 1998. For some years before this, the white-columned Biloxi mansion that was Davis's final home had served as a Confederate Veterans Home.