From a 1991 Paris Review interview (which is worth reading in full):

I write on an old Royal typewriter, a beauty! I bought it secondhand in 1964, before I started The Johnstown Flood, and I’ve written all my books on it. It was made about 1941 and it works perfectly. I have it cleaned and oiled about once every book and the roller has to be replaced now and then. Otherwise it’s the same machine. Imagine—it’s more than fifty years old and it still does just what it was built to do! There’s not a thing wrong with it.

I love putting paper in.

I love the way the keys come up and actually print the letters.

I love it when I swing that carriage and the bell rings like an old trolley car.

I love the feeling of making something with my hands.

People say, But with a computer you could go so much faster. Well, I don’t want to go faster. If anything, I should go slower. I don’t think all that fast.

They say, But you could change things so readily. I can change things very readily as it is. I take a pen and draw a circle around what I want to move up or down or wherever and then I retype it.

Then they say, But you wouldn’t have to retype it. But when I’m retyping I’m also rewriting.

And I’m listening, hearing what I’ve written. Writing should be done for the ear. Rosalee reads aloud wonderfully and it’s a tremendous help to me to hear her speak what I’ve written. Or sometimes I read it to her. It’s so important. You hear things that are wrong, that call for editing.