Complex sentence: The Cardinal is also responsible for the effort to restore Baltimore's Basilica of the National Shrine of the Assumption of the Blessed Virgin Mary, America's First Cathedral, the cost of which was financed entirely through private donations.
Split into simpler sentences: The Cardinal is also responsible for the effort to restore Baltimore's Basilica of the National Shrine of the Assumption of the Blessed Virgin Mary, America's oldest Cathedral. The cost of which was financed entirely through private donations.