“American Family” is an ambitious play, a laudable and moving production, even if it’s not a particularly subtle one. The story focuses on a family torn apart by the persistently thorny issues of race relations in America, specifically grappling with interracial love and marriage in the mid-1960s South — a time when such relationships were still illegal in many states.

The play is a brand new commission for Park Square Theatre (a Knight Arts grantee) — written by and co-starring noted playwright Carlyle Brown and directed by Twin Cities theater veteran Marion McClinton. It’s a small cast with an able assortment of local talent: Noël Raymond (co-director of Pillsbury House Theatre) and Gavin Lawrence play the tale’s central couple, a white divorcee (Laura Collins-Richardson) and her new African-American husband (Jimmy Richardson). Actor John Middleton deftly captures the slouched, unctuous menace of Laura’s estranged ex-husband, Billy Collins. Likewise, Brown and the wonderful Greta Oglesby are convincing as Jimmy’s parents, hardscrabble Alabama farmers, Sonny and Martha Richardson. Finally, Megan Fischer and Tracey Malone jointly portray the protagonist and narrator, Mary Ellen Collins-Richardson — Laura’s daughter by her first marriage, removed from her custody by her ex-husband after the courts declared her an unfit mother due to miscegenation.

We meet Mary Ellen at two pivotal moments in her life — as a girl of just nine years old (Fischer), innocent, happy and well-loved, but not for much longer; and then again, as a troubled young adult (Malone) returned to her childhood home, seeking out the half-brother she’s never known (played by Michael Terrell Brown).

The first act, which takes place inside the now-grown Mary Ellen’s memories of 1964, at once establishes for the audience and tears asunder the newly formed family at the play’s heart. And this is where the play shines, offering a genuinely felt portrait of the making of a modern, multiracial family. Here Brown’s script inventively captures both the sweep of the historic cultural struggle in the background and the intimacies of the human relationships at the story’s center, complete with all the awkwardness and unexpected moments of graciousness that combine to knit relationships over time. When Mary Ellen is torn from her mother’s arms at the close of act one, such a fully fleshed assortment of characters have been created, you’d have to be made of stone to remain unmoved.

The second half of the play is set in the “present” of 1979, when Mary Ellen returns to the idyllic environs of her childhood to meet her brother. At this point, the story becomes a stark portrait of robbed innocence: we find out what became of the optimistic girl Mary Ellen once was, precisely how she was damaged over the years by her abusive father and the self-destructive lengths to which that path led her.

The story feels a bit leaden in act two, sacrificing some of the authenticity and complexity of its characters for the sake of landing an unequivocal message about toll of the injustice; plot and characterization veer perilously close to two-dimensional, “After School Special”-style exaggeration in service of that aim.

But quibbles aside, “American Family” is a play whose merits more than compensate for this unevenness. In an essay published with the program, Brown is quoted as saying, “This is a new kind of play for me. I’ve never written a play with a female central character. And I’m exploring the American identity from an African-American perspective, but the central character is white .… I thought it would resonate with [the Park Square] audience … [because] we can better look at issues when we can see ourselves on stage.”

“American Family,” written by Brown and directed by McClinton, is on stage through April 7 at Park Square Theatre, 20 W. Seventh Place, St. Paul, Minn. For ticket details and more information: http://www.parksquaretheatre.org/www/pst-showpage-american-family.php