The Cathedral Basilica of Saints Peter and Paul in Philadelphia, Pennsylvania is beautiful inside and out (except for the surgical abortion signs on the lawn, but forget that part for now).
Construction began in 1846, and as the bishop admirably wanted to avoid going into debt to build it, construction continued all the way through 1864.
You may note the lack of windows, which is by design to prevent vandalism. This seems an odd focus when building a church, if you ask me, though apparently anti-Catholic sentiment was running strong in Philadelphia at the time of its construction.
Its grand Palladian façade is made of brownstone, and there is a large aqua oxidized-copper vaulted dome atop. The cathedral is said to have been modeled after the Lombard Church of Saint Charles (San Carlo al Corso) in Rome, though I honestly cannot see any resemblance. It is in the Neo-Classical style of the Italian Renaissance inside and out.
It is the largest Catholic church in Pennsylvania, with the main sanctuary seating 1,000 worshippers, and another 500 possible when temporary seating is employed. It is 300 feet long by 136 feet wide, and, including the gold cross on top of the dome, it is 209 tall.