The eastern entrance to the 4th Avenue/9th Street subway station — shuttered since Richard Nixon was in the White House — was finally reopened yesterday, part of a massive MTA rebuilding effort in Brooklyn.

For the first time in 40 years, straphangers east of the station in Park Slope can avoid crossing multiple lanes of traffic to get to the F/G train station, which serves roughly 11,400 passengers a day.

Other station improvements include new lights, floors, walls and turnstiles.

But the historic arch — one of the station’s signature architectural features — still needs to be restored.