These words are literally writ large on New York's 8th Ave. Post Office:
Neither snow nor rain nor heat
nor gloom of night
stays these couriers from
the swift completion
of their appointed rounds.
Now that's what you call a mission statement... though apparently, it's not. Nor a slogan, a motto, a credo nor a creed; not even a brand truth.
It's actually largely an architectural detail added by William Mitchell Kendall when he was designing what's now the James A Farley Post Office Building in 1912. So the US Postal Service has this wonderful language and inspirational sentiment incised in its stone, but it seems, doesn't claim it as an institutional manifesto. Many a brand would savage you to own such a declaration. No matter, it's magnificently realised, chiselled into the architrave - and a powerful expression of intent.
Coming across it for the first time recently - and struggling to photograph it - one would have to admire the chutzpah to strike it out so proudly across the whole length of the facade. Though it must be acknowledged, Seinfeld's Newman was less taken by it.