For all intents the structure is actually less than 20 years old
Wiki has a really good article on the old girl.
http://en.wikipedia.org/wiki/USS_Constitution#1995_reconstruction1995 reconstruction
Photo of a ship at sail with two escorts as navy jets fly overhead
Constitution sails unassisted for the first time in 116 years
Constitution entered dry dock in 1992 for an inspection and minor repair period that turned out to be her most comprehensive structural restoration and repair since she was launched in 1797. Over the 200 years of her career, as her mission changed from a fighting warship to a training ship and eventually a receiving ship, multiple refittings removed most of her original construction components and design. In 1993 the Naval History & Heritage Command Detachment Boston reviewed Humphreys' original plans and identified five main structural components that were required to prevent hogging of a ship's hull,[204] as Constitution had at this point 13 in (330 mm) of hog. Using a 1:16 scale model of the ship, they were able to determine that restoring the original components would result in a 10% increase in hull stiffness.[205]
Using radiography, a technique unavailable during previous reconstruction, 300 scans of her timbers were completed to find any hidden problems otherwise undetectable from the outside. Aided by the United States Forest Service's Forest Products Laboratory, the repair crew used sound wave testing to determine the condition of the remaining timbers that may have been rotting from the inside.[204] The 13 in (330 mm) of hog was removed from her keel by allowing the ship to settle naturally while in dry dock. The most difficult task, as during her 1920s restoration, was the procurement of timber in the quantity and sizes needed. The city of Charleston, South Carolina donated live oak trees that were felled by Hurricane Hugo in 1989, and the International Paper Company donated live oak from its own property.[200] The project continued to reconstruct her to 1812 specifications while she remained open to visitors, who were allowed to observe the process and converse with workers.[204] The twelve million dollar project was completed in 1995.[206]