Travelling nearly 10,000 miles by train, British photographer Katie Edwards crossed the United States capturing the landscape through a window.

The journey, from New York to San Francisco, via Chicago, Los Angeles and Seattle, resulted in 20,000 photographs taken during 180 hours on the rails.

“I had assumed that the world was going to be full of exquisite moments and my job was simply to surrender to the train, its speed, direction and frame,” Edwards says.

But the reality saw dirty train windows and reflections that obscured the views.

Taking the photographs in a vestibule at the end of a carriage, Edwards taped a large bag to the opposite window to reduce the glare – though the train conductor was not so happy.

Towards the front of the train, her father, John, acted as a spotter, giving Edwards a brief warning of upcoming photo opportunities.

At one point, John shouted: “Deer,” through the phone.

“I wasn’t quick enough,” Edwards says.

“But if there was one deer, there would be more.

“Finally, my concentration paid off and I secured a shot of two little deer almost touching noses in front of a huge cliff face.

“I was very happy.”

A more unexpected message from John was simply: “Moony.”

At first, Edwards thought she had misheard but set about taking pictures anyway.

“I quickly looked back at my photos,” she says.

“There was indeed a perfect line of bottoms opposite the train.”

But while photographing the farmland of Illinois, Edwards missed a frame she wished she had shot.

“I had been standing at the window for hours, my feet were hurting and my eyes were glazing over,” she says.

“And an exquisite moment passed me by.

“A queue of army tanks were waiting at a crossing and, if that wasn’t enough, a baby deer was looking up at the first tank in fear or curiosity or both.

“Gone in a second – if I’d been concentrating, I could have caught that moment.”

Edwards describes each picture as a fragment of a larger narrative.

“The journey itself became a storyline that traversed different geographical and cultural landscapes,” she says.

An eight-hour delay meant Edwards found herself amid large open plains as the light faded towards the end of the day.

“I was able to see for hundreds of miles on either side and this created bizarre effects with the light as it hit specific strips of land in the expanse,” she says.

Returning to the UK meant long days of editing, reducing the thousands of pictures to just 20 for an exhibition at London’s Observatory Photography Gallery.

Laying all the images together created panoramic views of fields and stations, each elongated or contracted depending on the speed of the train.

“Looking at the mosaic of all the pictures, you can see strata as you move from one landscape to another,” Edwards says.

“This image was the very last one that I found in my search, discovered three months after it was taken, it almost didn’t make the exhibition.

“The rungs of the ladder make me feel as if I could climb the mountain in just a few steps.”

Portrait of America is at London’s Observatory Photography Gallery from 26 September to 25 January.

More of Edwards’s work can be seen on Instagram.