- There was the question of whether it was even possible to build a bridge across the Golden Gate.

It is extremely difficult for lots of reasons.

The engineering and logistical challenges were profoundly complicated.

(gentle music) - I think it's one of the most daunting geographic areas to build a bridge.

It was beyond people's imagination how difficult it was.

The Bay and the Pacific meet at the Golden Gate.

All of the water in the Bay empties into the Pacific every three days, and the tides coming in from the Pacific have to channel themselves through this hourglass structure and are quite awesome, (gentle music) and a fellow named Ellis, actually, designed the bridge.

(gentle music) - [Expert 1] Strauss hired Charles Ellis to work out the practical engineering of building the bridge.

He doesn't always receive the credit, but his calculations and his designs made it possible.

- Did people think it was an engineering marvel to build this bridge?

- A lot of people thought you couldn't build the bridge.

The unique geography of the site presents some challenges and the distance across the strait is quite large, and so that distance necessitated a much bigger bridge than anything that had been contemplated up to this point in time.

Some people said that it was too big to overcome.

It's also a very harsh site.

Mother Nature introduces lots of challenges.

The geologists at Stanford said that the rock under the South Tower is not strong enough and the South Tower's gonna topple over.

A lot of very learned people challenge the viability of building at this site.