Chances are you crossed a bridge today,

went through a tunnel

or skipped the stairs for the escalator.

Maybe you took the subway

or passed by one of the great monuments to American history.

Feats of engineering are all around us

and at American Experience we 're putting them on the map,

so to speak.

Once again, we 're setting out to map America.

This time we 're exploring the major building projects

that has transformed cities and towns across the country.

and in turn have transformed the way we live and work.

Did you know that before 1910

people shuttled on and off Manhattan on ferries?

Today millions of people pour into the city

through underground tunnels to Penn Station and Central Station.

And speaking of Penn Station,

did you know this used to look like this?

Imagine San Francisco without the Golden Gate Bridge,

Washington, D.C., without the Washington Monument

or the US Capitol building

or the Colorado River before the Hoover Dam.

How did all these structures get built?

Explore the world around you with the Engineering Map of America.

Dig into the history of your hometown

or criss-cross America from Oregon to Georgia,

Michigan to Louisiana

with the online map,

or take it with you on your next vacation

or your walk around town.

The American Experience app lets you enjoy the view now and then.

Explore old and new photos.

Short videos tell the story of construction challenges and triumphs

behind the great feats of engineering.

Partners across the country are helping to tell the story

of America 's engineering history.

But we want your help too.

How has engineering transformed your city?

What's the most iconic building in your town?

Did a dam bring hydroelectric power to your region

or is a new bridge changing traffic patterns?

Upload your photos or videos and help us map America.

Log on or download the app now.