In 2005, writer-director Kenneth Lonergan assembled an all-star cast, including Matt Damon, Mark Ruffalo, Matthew Broderick and Anna Paquin, for "Margaret," his follow-up to the critically beloved indie film "You Can Count On Me."

Seven years later, "Margaret" finally arrives on DVD following a limited theatrical run at the end of 2011. The Fox Searchlight film spent nearly a decade on the shelf (read Joel Lovell's excellent piece on the "Margaret" post-production legal woes over at the New York Times website to find out what happened), but was greeted with open arms by those who saw it last year. Critics embraced the 150-minute film after its release, with many -- including The New Yorker's Richard Brody -- calling "Margaret" an ambitious masterpiece.

They aren't wrong. "Margaret" may very well be Hollywood's only macro/micro response to the tragedy of Sept. 11. On the immediate level, it's about a high schooler named Lisa (Paquin), a first-hand witness to a horribly violent accident on Manhattan's Upper West Side; on a larger scale, however, "Margaret" is about how a community deals with an unexpected tragedy.

With the film hitting DVD on July 10 (both the theatrical version and an extended cut are included on the disc), HuffPost Entertainment spoke to Lonergan about how Sept. 11 influenced "Margaret," why so few films have touched on the national tragedy in any significant way, and what the arduous post-production process taught him about filmmaking.

Where did you come up with the idea to write this screenplay?
The very initial kernel was the story a friend of mine told me in high school about this incident that happened to her. But it's a story that I've been interested in writing for quite a long time -- ever since she told me that, in fact. It sort of cropped up here and there over the years. The whole thing came to me very quickly and completely, which is unusual for me, in 1994. I wrote it all out in my notebook, which is also unusual for me. I was in the middle of writing three other things and I had several other things that were finished. It waited its turn. I started writing it in 2000. The main kernel of it, for me, is the idea of a young woman dealing with an adult situation when all she's got for tools are the equipment she uses to deal with life in high school.

"Margaret" really captures post-9/11 New York in ways that you don't usually see onscreen: The feeling of helplessness mixed with rage and anger. How much did Sept. 11 affect the script?
Quite a lot. When I started writing it -- the script was written between 2000 and 2003, so 9/11 comes right in the middle. It affected it immediately, of course. When I really plunged into this, 9/11 had happened. It became part of the script's consciousness as it became part of my consciousness as it became part of everyone's consciousness at the time.

I know you can't speak for other filmmakers, but why do you think so few movies have been made about the emotional reaction to 9/11?
I don't really know. Right after 9/11, as soon as the televisions went back on and the advertising returned to the city and country, and as soon as I started to see images of the airplanes flying into the building accompanied by dramatic music -- something that had been mercifully absent for a couple of weeks -- I sort of thought the country had maybe finally grown up. I was very disappointed to see that it had not, eventually. I was very surprised because everyone was saying, "How has this changed America? How has this changed the world?" I was asked to be part of an article in the Times -- they were asking a few New York writers how 9/11 had changed their writing. This was in January. I was like, "I don't fucking know. Are you kidding? Are you crazy? Something that size? I have no idea! I don't even know what happened. I don't know what's happening now. When's the last time the World Trade Center blew up? What are you talking about?" It's the television phenomena of instantly wanting to brand the decade. "What's this decade going to be like?" What's the style? They didn't do that until the '60s or '70s. In the '40s, they didn't talk about the '30s; F. Scott Fitzgerald talked about the '20s a lot, but he was sorta of the first to do that. They didn't used to do that. I think whatever reaction I had was unconscious, but my conscious reaction was, "I don't know." It's so enormous.

I can't answer for anyone else. I think some people have written about it and there were some films about it, but ... I honestly can't answer that. I'm actually a little surprised. I don't think we know what to make of it. The war started against Iraq so quickly, and that became the controversial issue. Al Qaeda became a side issue. "Oh, yeah, we know they're bad, but we don't like this war." Or, "Oh yeah they're terrible and we support this war." But the whole superstructure of it, and what it meant to live in the United States, got swept under the rug.

We don't make a lot of political films in the United States. I don't think art and politics mix very well anyway, except on the human level, and that's all I have to offer: the human level. Oliver Stone made "World Trade Center" and "W.," and I admire his boldness but not his thoughtfulness, of which I think he has none. His response to 9/11 was that it as our fault. I find that to be sick.

You finished "Margaret" in 2006. Do you think the lengthy delay between completion and release was beneficial to how people viewed the film, especially with how it handles 9/11?
I haven't thought of that, but maybe so. Maybe it's a good thing to remind people of what it was like. I guess there wasn't a lot of films about daily life here. Or, if there were, they were films I didn't see. I'm not an authority to say. For all I know there were two-dozen films that I missed. I know there were a number of Iraqi war films, but just in terms of living in the city -- there was a lot of theater about it. I think it would be fine if it came out then. I'm appreciative of the nice things people have written, but I read somewhere, "While it's great, it seems a bit dated." Are you crazy? It's dated because it takes place seven years ago and was shot six years ago?

After the experience making "Margaret" -- and the tortured post-production process to get it onscreen -- what would you differently on your next film?
I don't know [laughs]. I think I would try to find a way to better isolate the work process from the usual arguments that go on in any film situation. Find a way to not mix the two together, if possible. Nothing that unusual happened. It was a difficult film to edit; it was very challenging, it's a very big movie. It's very normal for there to be differences of opinion in the editing phase. I think I would try to plan better, for myself. I don't think anything was planned poorly, but for my own sanity, to have a system in place. So I could work separately from the conversations that are necessary, ultimately, for the good of the movie. It's not a one-man job, no matter what they say. There's a lot of collaboration. Some films are easy to do, some films are difficult to do. They all run into their problems. Sometimes the problems make the film better. I'm not 100 percent sure I would change anything.