The present episcopal see of the diocese, St. Peter's Cathedral in London, Ontario, was built in a French Gothic Revival style from 1880 to 1885.

It was raised to the status of a minor basilica by Pope John XXIII in December, 1961.

The Diocese covers the counties of Middlesex, Elgin, Norfolk, Oxford, Perth, Huron, Lambton, Kent and Essex.

[1] The diocese also runs St. Peter's Seminary, which is now affiliated with the University of Western Ontario.

[2] Following media coverage of the list, the Diocese waived confidentiality of their previous settlements.