By this website.............they missed the Wash monument from being its intended 555 ft in height..........by 4 and 21/32 of an inch................................the sides are 55 ft.............

The Washington Monument

Cornerstone Laid: July 4, 1848
Structural Construction Complete: December 6, 1884
Dedication Ceremony: February 21, 1885
Officially Opened: October 9, 1888
Style: Egyptian Revival
Architect: Robert Mills; Redesigned by Lt. Colonel Thomas Casey (US Army Corps of Engineers)
Height: 554 feet 7-11/32 inches* (169.046 meters*)
Dimensions: 55 feet 1-1/2 inches (16.80 m) each side at the base, tapering to 34 feet 5-5/8 inches (10.5 m) at 500 feet level (top of shaft and bottom of pyramid); the foundation is reportedly 80 feet by 80 feet