On Friday night, crews began shutting down lanes on the existing bridge, and just after 1:30 a.m. Saturday the first cars made their way across the new span connecting Rockland and Weschester counties.
The $4 billion, twin span crossing has been the largest infrastructure project in the nation.
After years of construction and a couple of days of fanfare, some motorists got up early Saturday, specifically for a test drive.
"I just came, turned around and I'm going back. Beautiful bridge," said Regan Kelly.
The original Tappan Zee Bridge has outlasted its 50-year lifespan by a decade, unable to accommodate the 140,000 cars that cross each day.
The new bridge will have wider lanes and a bicycle/walking path. And the 419-foot towers that support the stay cables are a highlight.
"I took a picture. I know I'm not supposed to be on my phone, but I took a picture anyway," said motorist Frank Fishetti.
"Watching it get built, it's beautiful," said motorist Ken Fuirst. "Driving over it was an exciting experience this morning."
In a few months all traffic will be moved to the new span while the old Tappan Zee is dismantled and the second span completed.
The entire project should be wrapped up by spring.