Arch With PDM On The Cross-Brace
When they reached a point near the completion of the Gateway Arch, they had to stabilize it with a cross-brace. The cross-brace had the letters PDM on it, standing for Pittsburgh-Des Moines Steel. This "advertising" caused a great deal of controversy. So they made PDM take the letters down.
Arch Is Completed Without PDM On The Cross-Brace