Skydeck Chicago, the observation deck atop Willis Tower, the tallest building in Chicago, is celebrating its 50th anniversary.

It was designed as a gift to the city of Chicago; an observation deck on the top of what was then the world’s tallest building and still called Sears Tower.

This summer, the Willis Tower Skydeck turned 50 years old.

The view from more than 1,300 feet provokes a common reaction – a mix of wonder, shock, and sometimes a little fear. People have been having those reactions for 50 years.

“June 21st, 1974, Skydeck opened to the public. It was about a year after the building opened in 1973,” said Skydeck Chicago general manager Randy Stancik.

The observation deck was part of the Willis Tower’s original plan to give back to the city.

Skydeck has changed quite a bit since those early days. It now features the Ledge, which opened in 2009, featuring glass and steel boxes that extend out from the sides of the building, allowing visitors to look down through their glass floors to the ground 1,300 feet below them.

There are also recent additions like animated maps and a full Chicago museum on the bottom floor.

Stancik said the views and the memories will only get better in the next 50 years.

Stancik expects to see 1.3 million visitors at the Skydeck this year. The deck is on the 103rd floor of Willis Tower – 1,353 feet in the air, making it the highest observation deck in the United States.

The Skydeck celebrated a little differently than most. There was a cake, but it was more than 1,300 feet above Chicago.