At the time of the film's production in 1964, Julie Andrews was just 29 years old. Initially, Andrews was hesitant to accept the role. The star's breakthrough Disney film "Mary Poppins" was still in production, and she was worried about playing another "wholesome nanny" role, Biography reported.

Other actresses, including Audrey Hepburn, Doris Day, and even Grace Kelly, were considered for the role, but in the end, Andrews was screenplay writer Ernest Lehman's first choice.

It ended up being the right one — Andrews received an Oscar nomination for best actress at the 38th Academy Awards.

Andrews, 89, has had a prolific acting career. Among her roles, she played Queen Clarisse in the "Princess Diaries" movies, although she revealed she likely won't be returning for the third film.

Over the past 10 years, she's mostly voice-acted, appearing as characters in the "Shrek" and "Despicable Me" movies, among others. Andrews also voices the narrator and elusive gossip columnist Lady Whistledown in "Bridgerton." 

"She was at the top of our list for Lady Whistledown," "Bridgerton" showrunner Chris Van Dusen told Oprah Magazine in 2020. "We offered her the part, sent her the scripts, not thinking anything would really come of it. But surprisingly she read the scripts and fell in love with them."

"Bridgerton" series author Julia Quinn said she was shocked. "When they told me I legitimately stopped breathing," she said. "I mean, I should be dead."

Speaking to Vanity Fair in 2022, Andrews said her pivot to voice acting over the last decade has been "wonderful."

"I don't have to get hair and makeup anymore. I just go into the studio and do my voiceovers," she said. 

Plummer also recalled being hesitant about the script, "because it was so awful and sentimental and gooey," he told the Hollywood Reporter in 2011. "You had to work terribly hard to try and infuse some minuscule bit of humor into it."

However, Plummer's background as a dramatic actor made him perfect for the role in the producers' eyes. Despite his acting chops, his singing ended up being dubbed in the final version with singer Bill Lee's voice, NPR reported.

He was nominated for three Academy Awards, ultimately winning the best supporting actor award for "Beginners" in 2012. At 82, he became the oldest actor to ever receive an Oscar.

In 2019, Plummer starred in Rian Johnson's "Knives Out" opposite Chris Evans and Ana de Armas.

However, his part as Captain Georg von Trapp in "The Sound of Music" is arguably his most fondly remembered role, though he frequently shunned the movie in later years.

"I was a bit bored with the character," Plummer told The Boston Globe in 2010. "Although we worked hard enough to make him interesting, it was a bit like flogging a dead horse. And the subject matter is not mine. I mean, it can't appeal to every person in the world. It's not my cup of tea."

Despite not liking his role in the movie, Plummer remained "the best of friends" with his costar Julie Andrews for decades, she told ABC.

On February 5, 2021, Christopher Plummer died at his home in Connecticut with his wife, Elaine Taylor, by his side. He was 91. 

Rather than being 16 going on 17, the actor was actually 21 years old when she played the eldest von Trapp child in her breakout role.

The Telegraph reported that Carr's mother recommended her to a casting agent for "The Sound of Music," saying, "She's 21, but she could pass for 16."

The actor was working as a physician's assistant at the time and had no theatrical or musical training. However, she captivated the casting agents with her beautiful voice and appearance.

Carr starred in the musical "Evening Primrose" in 1966, the year after "The Sound of Music" was released.

"It was hard to have your first role as the high spot of your career," she told the London Daily Telegraph, The Washington Post reported. "I felt smothered by Liesl. She began to feel like my evil twin, the perfect one that everyone loved."

While taking a short break from touring the world promoting "The Sound of Music," Carr met and married her husband, Jay Brent. Carr continued acting for a while, but after becoming a mother to two children, she decided to leave Hollywood and focus on building an interior design company. She and her husband divorced in 1991, after which she wrote her autobiography, "Forever Liesl."

On September 17, 2016, Carr died due to complications from a rare form of dementia at the age of 73.

When "The Sound of Music" was released, Nicholas Hammond was 15 years old. His mother, Eileen Bennett, was also an actor, but the one who indirectly influenced him to go into acting was Julie Andrews herself. 

"I saw her onstage in 'My Fair Lady' when I was nine and I made a decision that night that I wanted to do what that lady does," Hammond told Parade in 2013.

Hammond was the first actor to play Spider-Man in a live-action production of the comic. Born in 1950, he is also the only actor born before the character first appeared in a comic book in 1962.

Hammond, 74, was born in the US but moved to Australia in the mid-1980s. The actor now lives in Sydney where he works as an actor, screenwriter, and director. He's also remained close with his "The Sound of Music" costars, especially the other von Trapp children.

"We bonded because, for all of us, and particularly the seven kids, it was an extraordinary experience as a young person to go through — where one day you're an unknown child actor and literally the day after the film opens, we were the seven most famous children in the world," he told Parade.

The film was released when Menzies-Urich was just 15 years old.

Though Louisa didn't have much of a storyline, Menzies-Urich was able to display her ballet background during the performance of "So Long, Farewell."

The series, which was a spinoff of the movie of the same name, only ran for one season between 1977 and 1978. Menzies-Urich continued to act until 1990, mostly appearing in television shows and TV movies.

She died in 2017 at the age of 68. Her son, Ryan Urich, shared the news.

"She was an actress, a ballerina, and loved living her life to the fullest," Urich said, USA Today reported.

Chase had a short-lived career as a child actor. Following his breakout role as Kurt von Trapp at 15 years old, Duane Chase acted in the family films "Follow Me, Boys!"  and "The Big Valley." 

After "The Sound of Music," Chase briefly fought fires with the forestry service. Later, in 2020, he volunteered to drive supply trucks down to Southern Oregon to fight the wildfires sweeping across the state and California. 

Now 74, he lives in Seattle and works as a computer software analyst and designer for oil and mining companies.

Prior to landing the role of Brigitta, Cartwright acted in the 1950s TV series "The Danny Thomas Show."

"Thousands were interviewed to play the parts of the von Trapp children, and when I got word I had been cast, I was so excited," she wrote on her website. "Danny Thomas released me from the last show of the 'Danny Thomas Show' season so I could begin working on this movie. For that, I am so grateful because he didn't have to do that."

Angela Cartwright, now 72, had a relatively successful acting career following "The Sound of Music." Her acting credits include roles in "Lost in Space," "My Three Sons," and "The Love Boat."

She's continued acting and voiced the role of Edna Platt in a 2022 episode of "Adventures in Odyssey."

Debbie Turner grew up in a showbiz family and moved to California in the 1950s. She was involved in TV, commercial, and print modeling work before landing the role of Marta in "The Sound of Music."

Turner, 68, lives in Chanhassen, Minnesota, and has operated her floral design company for over 30 years, according to her website.

During the start of the COVID-19 pandemic, Turner paid homage to her "The Sound of Music" roots with a new business venture: making face masks based on the iconic curtains used to make the children's play clothes in the movie.

She also makes and sells scarves made out of a similar fabric to the one used in the movie. 

Karath had a successful career as a child actor in the early 1960s before landing her role in "The Sound of Music" when she was 5.

At the time of the movie's filming, Karath couldn't swim, which made the boat-flipping scene challenging. 

"The little one can't swim, please fall to the front of the boat so you can get to her quickly," Andrews told ABC News the directors asked her. "Of course, I went to the back of the boat."

Another von Trapp child ended up having to lift Karath to safety.

After "The Sound of Music," Karath had roles in television shows like "Dr. Kildare," "Lassie," "Lost in Space," and "The Brady Bunch."

After graduating from the University of Southern California, the actor, now 66, moved to Paris to study art history and model. She married her husband, Philippe L'Equilbec, and returned to the US. However, she took a lengthy break from acting to raise their son.

In 2005, the cast of "The Sound of Music" reunited to share what they were up to now. At the time, Karath said she was resuming her acting career in Los Angeles, but she hasn't had any roles since 1981.