You're doin' fine, 'Oklahoma!'

While he grew up in Southern California, Zach Johnson spent his summers in Oklahoma from the age of 3 to 13 — which makes the Rodgers & Hammerstein musical “Oklahoma!” an appropriate choice for his directorial debut.

“I cannot lie — Ihave sung ‘Oklahoma’ in Oklahoma,” Johnson said.

And he wouldn’t be the only one. The musical’s title number — with its agricultural imagery and promise for a prosperous future — was named Oklahoma’s official song in 1953, prompting many Oklahomans to sing “Ayipioeeay” at the tops of their lungs.

"I get chills just thinking about the song,” said Johnson, who is also the choreographer for the show, which begins a monthlong run at the San Luis Obispo Little Theatre on Friday night. “You don’t get a lot of songs like that, where you’re literally just describing all the positive things that happen around you.”

The music, of course, is what made “Oklahoma!” such a groundbreaking musical.

The play, written by Richard Rodgers and Oscar Hammerstein II in 1943, approached the musical, which began with “Showboat” in the 1920s, and took it a step further, allowing the music to tell parts of the story.

“The song ‘Say We’re in Love’ is in there for that specific reason,” Johnson said. “To say, ‘I’m not going to tell you how much I love you, and you’re not going to tell me you love me, but we’re singing how much we love each other.’ And from that point on, almost every musical they did together had a song that does that same thing.”

The musical, set in the Oklahoma Territory in 1906, features a boy-seeksgirl plot, with cowboy Curly McLain pining for Laurey Williams, described then as “an independent woman.”

“She’s headstrong and she’s a big personality,” said Lauren Moore, who portrays Laurey. “But in the end it’s all about ending up with the man. I think today an independent woman might not want to go that way, but I think a lot of people can relate to her character.”

The 1955 movie adaptation, starring Shirley Jones and Gordon MacRae, was also hugely successful. While the boisterous numbers from the film come off a bit cornball, people who want to see “Oklahoma!” have expectations. So you can’t mess with the formula too much, said Kevin Harris, the Little Theatre’s managing artistic director.

“I can’t think of anything worse than an ironic ‘Oklahoma!’ ” Harris said. “There’s a reason it’s been around for 60 years — those scenes work.”

While tinkering with the essence of the musical might backfire, the cheese factor can be lessened, said Marcus DiMaggio, who plays Curly — as he did when he was a junior during a run at Coast Union High School.

“I did OK with it in high school, but I’m more mature now, and I’ve had the ability to think about the role and analyze the character a lot more,” he said. “So I’m enjoying being able to take a more realistic take on it.”

Staples like “Oklahoma!” provide abalance for the Little Theatre, which has also tried to integrate edgier shows into the mix. And as the Little Theatre celebrates its 65th anniversary, Harris noted that “Oklahoma!” was performed by the theater 50 years ago at the Madonna Inn.

In fact, Phyllis Madonna, who helped create the iconic inn, portrayed Laurey.

“I used to sing with a band at the inn,” Madonna said. “And some of the people that were with the Little Theatre heard my singing, and they felt like my voice sort of fit the part of Laurey.”

The musical, already nearly 20 years old then, was a hit, as acrowd packed the still unfinished Gold Rush Steak House for six shows.

“I can recall so many, many faces out there, as I performed,” Madonna said. “And it was such a small town 50 years ago that everyone knew everyone else.”

That San Luis Obispo is still a small town helps locals relate to a show like “Oklahoma!”

“I feel like the setting is close to the area as far as the agricultural community,” said Moore, who graduated from Paso Robles High School before going to Cal Arts and now Cal Poly, where she is working on a vocal performance degree.

But mostly the musical’s enduring success boils down to the songs.

“I’ve had very little in my head besides ‘Oklahoma’ for the past three weeks or so,” said DiMaggio, who was coaxed to audition for the role by his sister, Kerry DiMaggio, who portrays Ado Annie. “It’s definitely stick-in-your head kind of music.”

DiMaggio, who went on to earn a global cultures degree after high school, opens the show with the popular number “Oh, What a Beautiful Mornin’.” Other recognizable numbers include “People Will Say We’re in Love,” covered by artists such as Ella Fitzgerald, Frank Sinatra and Ray Charles, and “The Surrey with the Fringe on Top,” which was memorably performed in “When Harry Met Sally.”

Still performed regularly nationwide, “Oklahoma!” put the state of Oklahoma on the map for theatergoers — many of whom will never actually see the state.

Even Johnson, who arrived at a recent rehearsal wearing cowboy boots and chewing Grizzly dipping tobacco, hasn’t been to the family farm that much since adulthood. But his work on “Oklahoma!” helps stir up memories of riding horses, medicating cattle and watching the weather.

“The thunderstorms in Oklahoma are some of the best I’ve ever been around,” he said.