Errors in unexpected places

Sometimes, an error in a public sign surprises me because of the context. I visited Washington late in May and happened to attend an event at the St. Regis, a venerable hotel near the White House. I spotted this sign outside:

I wonder why the sign's writer made the mistake of using 's to make the proper name Astor plural. What is even more surprising is that no one stopped the mistake before the sign went up.