I’m not actually a member of the Steppenwolf ensemble – to be invited you usually have to do more than act and I just act – however this is my eighth play with them and I’ve known some of the company members since the early Eighties, they’re good friends. I sort of consider myself like the eccentric aunt: I’m not in that nuclear unit but I’m certainly part of the extended family. The Chicago theatre community overall is sort of an extended ensemble. It’s not like New York where there are so many more actors vying for more commercial theatre roles. In Chicago the theatre scene is mainly not-for-profit and most of us float from theatre to theatre and form little mini ensembles.

I think our ensemble style is very generous. Nobody is grabbing the attention from anybody else, everyone wants to give their partner on the stage the opportunity to lift what needs to be lifted out of the scene in service to the playwright and the play. We’re all focused on that and I think, in that regard, we’re pretty selfless.

In spring 2006 I got a call from the Steppenwolf casting director saying that Tracy Letts needed to hear this new play he had written read. I loved Tracy and said I’d be happy to help, but after they sent me the script for August: Osage County, I called back and said I didn’t think Tracy would get what he needed from me because I have no experience using or being around people using pharmaceuticals. They said it didn’t matter, he just needed to hear the words.

So I went in and read it and was really so devastated by the play that I couldn’t speak afterwards. I was so upset that, when I got a call two days later offering me the part, I turned it down. Not only did I find it emotionally upsetting, I was worried about the physical aspects. I was having a lot of problems with my knees and my back at the time. They waited about a month for me to change my mind. I finally decided it was impossible to turn this down. If you turn these kinds of challenges down, you hate yourself because you’re just a coward. So I started seeing a physical trainer and worked very hard in preparation for six months before we started rehearsals in May 2007.

We ran the show all that summer in Chicago to an amazing reception with people lined up on their lawn chairs in front of the theatre from as early as eight in the morning to try to get the day tickets. Towards the end of the run, there were various commercial producers in New York who were very interested in taking it to Broadway. But none of us really wanted to go! We had chosen to live in Chicago, we had chosen not to live in New York and not to be in the commercial theatre world particularly.

My own reasons for that choice were highlighted when Tracy won the Pulitzer Prize for August: Osage County. Out of curiosity, I looked at how many other Pulitzer Prize-winning plays I’d done in my career. I’ve done eight. There’s no way in the world, living in New York, I could have done eight Pulitzer Prize-winning plays. The competition is just too fierce first of all. And secondly, of course, some of those classic plays were written back in the Fifties or Forties and they’re not being done in New York very often anymore.

So we didn’t really want to go to New York, but when it came down to it, we all knew we needed to do it. As a company, we wanted to expose people to Tracy’s work, to this really important play and to ensemble theatre as we do it in Chicago. The move was traumatic for most of us. Generally, New York producers ask for a six-month commitment, but ours asked us for eight months to take us through the Tony Awards. So five of us said yes to that – and the very day of the Tonys we left – while the other eight of the original 11 who went to Broadway stayed on longer.

By comparison, all of us wanted to come to London, and to the National specifically. So we’ve got nine of the original cast here. The National has such an international reputation for being a place where serious ensemble-type work is done, a place that really supports the art and artists. You’re so lucky to have a National Theatre here. In the States, money for the arts is being cut each year until it’s almost nonexistent so you have to fund your theatres through private donations and that’s very difficult.

The Whatsonstage.com Award nominations for August: Osage County are really heart-warming and humbling. We’re thrilled to have it be recognised this way on this side of the Atlantic. I’ve never been part of an award done in this way. Normally it’s a committee that picks the winner, but to have the public decide is lovely and exciting. The awards launch was so well received and attended – all of us came and were very impressed. There was such an energy and excitement. I am in awe.

- Deanna Dunagan was speaking to Terri Paddock

August: Osage County concludes its limited season at the National Theatre on 21 January 2009, running in the NT Lyttelton where it opened on 26 November 2008 (previews from 21 November). The production is directed by Anna D Shapiro. Other members of the original Steppenwolf company include Amy Morton, Rondi Reed, Marianne Mayberry and Jeff Perry.

Voting in the 2009 Whatsonstage.com Theatregoers\' Choice Awards continues until 31 January 2009.