Remember when: One Liberty Place opened

Philly's iconic tower officially opened for business 36 years ago today.

Why it matters: The building has come to define the city's skyline and served as a watershed moment with more skyscrapers coming in the years that followed.

Flashback: The 945-foot tower (excluding the spire) broke the so-called gentlemen's agreement that no building rise above the top of William Penn's hat atop City Hall.

• The building overcame opposition as some decried it would ruin the skyline and downtown character.
• A companion tower, Two Liberty Place, was completed in 1990.

Zoom in: One Liberty held the title as the city's tallest building for 21 years until 2008, when the Comcast Tower opened.

• It's now the third tallest in Philly and 39th in the U.S.

Between the lines: One Liberty's observation deck, which welcomed guests with unparalleled views of the city, closed permanently in late 2020 because of the pandemic.

• The 57th floor is vacant and available for lease, Kevin Mayer, director of the management company that runs One Liberty, tells Axios.