Complex sentence: The historical site is presently part of 6th street's bar district, and the upstairs loft where Letterman spent his last days has held many tenants during the last century, and currently is a bar named Peckerheads.
Split into simpler sentences: The historical site is presently part of 6th street's bar district. While the upstairs loft where Letterman spent his last days has held many merchants during the last century, it is currently a bar named Peckerheads.