Now you might think that you know the US.

But we're going to look at some maps that show it

in a completely different light, looking at some new data that

shows us how the US has built up over the last two centuries

from East Coast to West Coast.

Now cartographers love nothing more than new data

to put on maps.

And today, I'm with my colleague, Steve Bernard,

who is our master cartographer at the FT,

to look at some exciting new data recently released

by some academics at the University of Colorado.

And the first thing that I did with this data

was load it up quickly into our computerised mapping

software, our GIS.

And I zoomed in to Phoenix, Arizona,

just to have a little look at what the data says

about how Phoenix has developed over time.

And as you can see, in the early 20th century

we start to see these little black dots, which

are these individual pixels showing that that land has been

built up, right?

And as you can see, as we go through the 20th century,

you get this amazing picture of sort of growth.

And this city structure, the city shape of Phoenix,

really starts to come out.

And massive expansion in recent years.

So this was a very crude first attempt

at just looking at this data and thinking: does it

offer us anything useful?

Now I showed it to you, Steve.

And you got similarly very excited about it.

Yeah, the first time I saw it, I was looking over your shoulder

at this.

And I just thought, this is going

to be great to do for the whole of the US.

And this is all of this data showing

how the US has been built up since 1810

running as an animation now.

It's almost impossible to see to start with because you have

these very small little yellow pixels starting

to light up on the East Coast.

What just happened there?

So this is the railways flashing up as they were developed.

I got the data from the Library of Congress,

which had these amazing old maps, which they had digitised.

And I took these into the mapping software

and essentially traced them, every single railroad

from 1830s to 1890s.

And I needed to do them in stages

so I could show the development of the railroad from the East

Coast all the way to the West Coast.

So the yellow dots are the populated...

The yellow dots are the populated areas.

And the railroads are what you've just

flashed up on there.

That's interesting by itself because now we're

looking at two different data sets.

That's one of the powerful things

about this GIS, this computerised mapping software,

is the way that you can layer information on top.

So this might be a story that people are familiar with.

But this is the first time that they've seen it.

See it actually growing, yeah.

Then there's this whole pivotal moment

in the late 1860s when the first railroad connected the West

Coast to the East Coast.

And then you'll see the explosion

of population along the West Coast from that point on.

San Francisco, Los Angeles, further north into Seattle,

they are growing exponentially from that point on.

And the amount of railroads which are developed

is phenomenal.

Sort of unrelenting for the 60 years

or so from the 1830s to the 1890s.

When people think about travelling around the US now,

invariably people think about internal flights.

But back in this period, the railroad,

not only was it essential for getting about,

just from looking at these maps, we

can see that the railroad actually

helped to define the geography of the US.

So all of the areas that are building up

are building up based on the connections

that the railroad is making.

I mean, one of the things I thought

was very, very interesting looking

at some of these old maps was just how important

it was for people to have maps of these connections.

I mean, some of these maps here are really, really beautiful

maps.

But they're all talking about the connections.

This map here, Baltimore and Ohio Railroad,

is actually titled Shewing the Connection, this kind

of joining up of the cities.

It was an incredibly important part

of America's economic expansion.

This one here, the map of the Canal and Railroads of the US,

it's almost like a still from your animation.

It was painstaking tracing all of these

because obviously each map was slightly different at slightly

different projection, which means I had

to what's called georeferencing, which basically

turns this map into a rubber sheet

and allows me to stretch it inside the mapping software

to get it exactly into the projection

that we're using in the final animation.

After 1956, the US highways decided to build what is now

known as all the interstates in the US and which again just

enhanced the connections between the cities and made it easier

for people to mobilise and...

We're seeing highways on the animation where

although it's still allowing us to go east to west,

it's actually connecting up more of the country.

So the interstates are going to places

that not even the railroads necessarily were going.

So again, another layer of geography

telling us something a little bit

more about how the US was developing at that time.

The really interesting thing at this stage

as well, as you can already see, this

is so looking at 1970, just that difference

in density between the east and the west.

And then that kind of the open road

is really sort of the Midwest and out west.

You can see that.

And they look very, very sparse and isolated, the roads.

Whereas a lot denser connections over on the East Coast

- very, very stark.

A lot of that has to do with farmland areas in the Midwest,

which a lot of the area is given over to agriculture as opposed

to large cities.

So this is just showing exactly what areas of land

have been developed since 1810 through to 2015.

I added another layer showing when each parcel of land

was actually developed.

So before, the yellow just meant it's been built on.

It's been developed, yeah.

Now the colour is showing us when.

OK, so let's just interpret that colour ramp a little bit for us

here.

So the very earliest settlements are coloured yellow.

So we can see that's over on the East Coast there.

Massachusetts lighting up, for example.

Then it becomes red, orange-red, and through to purple.

So the more purple you see on the map

that's recent development.

Yeah, so a lot of the southern states, you can see,

are a lot more purple than obviously

the East Coast, Massachusetts, Boston, New York.

But still some of the orange on the West

Coast where Los Angeles, San Francisco,

were connected by those early railroads.

Just it's worth pointing out there

is still a lot of this data set -

that uncertainty is still a part of any big data set.

But this one in particular, there's still big chunks

represented by this teal sort of colour there.

Lots of a bit...

Michigan.

I guess some ambiguity.

I don't think that stops us thinking

that this is a very interesting way of looking at the US.

But it's kind of important to know

that no data set is perfect even when you put it on a map.

The thing that's fascinating for me

about using these computerised mapping systems

is that you can zoom in and zoom out freely.

And so we're going to go live into the GIS

now to have a look at some of this data.

So this is the application I used to create the animation

and the maps is called QGIS, which

is an open source software, which anyone can use for free.

One thing I looked at initially was 40 metro areas,

which had populations over a million,

and seeing how they had changed individually over the 205 years

that we have in the data set.

Chicago just grabbed my attention immediately.

A, because it's sort of a famous city

that everyone's fairly familiar with.

But the way that the city has grown in those early years,

you can really see very clearly, if I just

turn on the railways over the top,

how the early developments and settlements were

following along the railroads.

So this is using the same colour scheme that we were looking

at before.

So the yellow areas are the older areas,

the purple being more recent.

So that is fascinating.

You get this kind of...

Sort of spidery.

A spider's web sort of structure building out of the centre

of town.

That's instantly recognisable.

Absolutely.

Where else was interesting?

So what we're going to see here is

going to be the population growth from 1810

to 2015 in the downtown area.

It's the whole metro area of Phoenix-Mesa

because the census data doesn't cover that whole area

because obviously it's expanding all the time.

The map might show us when it was built.

But it doesn't actually show us an awful lot

about what's going on there.

The population data is going to show us actually

when did the people arrive.

Yeah, exactly.

Well, you'll get a sense obviously in the beginning.

As in your map, there's not a lot going on...

Dormant period for Phoenix.

The odd thing pops up in the late 1800s.

But after that, it's just an...

Now we start to see it go, yeah.

Carefully at the population map at the bottom chart,

that's at the bottom.

It really does grow exponentially in the past 40

years or so.

So the really interesting thing looking at animation

is actually there was a lot of growth in the built area

before you started to notice a real increase

in the population.

And in fact, most of the area had

been built on before the population density

presumably really ramps up.

So that's fascinating, being able to see

the sort of geographical spread of the city

relative to the sort of density of population

living in that area.

The population has pretty much tripled since the 1970s,

which is quite an explosion.

There are other cities as well...

There are indeed.

...worth looking at.

And in fact, the population charts

that you've created there are really, really interesting

because one of the things we see when we look at all

of the US, those major metro areas,

is that there's an interesting pattern repeated

across several cities.

Indeed, yeah.

A lot of the new cities like Phoenix, San Antonio, San

Diego, San Jose, they're the success stories

of this urbanisation.

But there are also some of the larger cities

that are being left behind.

If you look at this set of charts here,