An historic Hudson Valley icon that has seen better days is making way for a 21st century replacement.

After years of political wrangling, construction began on the current Tappan Zee Bridge in March 1952 and opened to traffic on Dec.15, 1955.

Built at a cost of roughly $80 million, the three-mile cantilever bridge serves as the main conduit between upstate and the New York City metropolitan region, connecting  South Nyack in Rockland County with Tarrytown in Westchester County.

The bridge is named after the American Indian tribe "Tappan" from the area and "Zee" is the Dutch word for "sea." In 1994, the name of former Gov. Malcolm Wilson was added to the bridge nearly 20 years after he left office.

State officials say traffic on the span has grown to about 140,000 vehicles per day, far more than the bridge was designed to support.

The Tappan Zee was designed to last only 50 years because of material shortages at the time of its construction due to the Korean War. It's now 12 years past its expiration date and showing signs of deterioration. In fact, the Federal Highway Administration has classified the current Tappan Zee bridge as "functionally obsolete."

So after years of public debate and discussions, construction started in 2013 on a new, state-of-the-art, nearly $4 billion replacement bridge.

Time-lapse video shows the steady progress on the massive "cable stay" bridge. It's eight concrete towers rising majestically over the Hudson River. The new bridge is expected not need any major maintenance for 100 years and has been named after former New York Gov. Mario Cuomo.

The opening of the first phase of the bridge replacement project is set for Aug. 25, 2017. That's when four lanes of Rockland-bound traffic will shift to the new 96-foot wide span.

Thruway Authority officials say Westchester-bound traffic will remain on the old bridge for "about a couple of months." The new bridge is set for full completion in 2018.