SF Presidio Arguello gate (1033)

Intricate military detail on the top of the gateposts at the Arguello entrance to the SF Presidio. As noted by James Ruddy (in the comments), "Essayons" is the Army Corp of Engineers motto. "Essayons" is French for "let us try" and reflects the role of the French Military Engineers in the creation of the U.S. Corp during the war for independence. The building in the image is the Corps Castle which is used as the emblem of the U.S. Army Corp of Engineers (USACE). The USACE website has an interesting set of photos from the corps involvement in the civil war:
www.usace.army.mil/About/History.aspx