Judy Garland, who would have turned 100 years old this week, wasn’t just billed as “the world’s greatest entertainer” – in her time, she really was.

Garland was much more than just little Dorothy Gale from Kansas who once had an adventure in far-off Oz. She spent 45 of her 47 years in show business, eventually making 34 feature films and more than 200 radio appearances, releasing 80 singles and 12 albums, making 60 TV appearances (including 30 of her own shows), and doing 1,100 concerts.

“She had the amazing ability to convey joy and pathos and humor and sincerity and honesty,” says author and Emmy-winning producer John Fricke (“Judy Garland: A Portrait in Art and Anecdote”), “yet by giving of herself on that level, she had no guard, no protective shield. She was a million percent vulnerable.”

Just watch 16-year-old Judy sing “Over the Rainbow” from “The Wizard of Oz” (1939) for that honesty; or “Get Happy” from “Summer Stock” (1950) for sheer joy; or the filmed-in-a-single-take “The Man That Got Away” from “A Star Is Born” (1954) for the undeniable pathos. Add “A Couple of Swells” from “Easter Parade” (1948) for that inimitable sense of humor and “Have Yourself a Merry Little Christmas” from “Meet Me in St. Louis” (1944) for a touch of wistful sincerity. And that’s just for starters.

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“She elevated the art of musical films to a level that did not exist before she became a screen presence,” says singer and American popular-music historian Michael Feinstein. “There is something about Judy Garland that communicates on a visceral level. People felt her truth and it made them feel better about themselves and their lives.”

Placed under contract at MGM in 1935, she rocketed to stardom with “The Wizard of Oz,” the musical fantasy that, some will argue, is the most beloved movie of all time. It won her a special Oscar (“outstanding performance as a screen juvenile”). The film’s annual television showings, which began in 1956, and video releases starting in 1980, continued to remind succeeding generations of the original Garland magic.

MGM producer Arthur Freed’s belief in Garland’s talent led to a series of musicals, first with Mickey Rooney (“Babes in Arms,” “Strike Up the Band,” “Babes on Broadway,” “Girl Crazy”) and later in the 1940s with Gene Kelly (“For Me and My Gal,” “The Pirate”) and Fred Astaire (“Easter Parade”).

MGM dropped her in 1950, but she quickly bounced back, both on radio (especially with her friend Bing Crosby) and in sold-out concert appearances in Europe and the U.S.

More dramatic screen appearances for other studios followed, none more significant than her powerfully emotional role as Vicki Lester opposite James Mason in “A Star Is Born,” earning her sole Oscar nomination as best actress — which, according to most observers in the decades since, she should have won.

She received another nomination, as best supporting actress for her role as a reluctant, anguished witness in Stanley Kramer’s “Judgment at Nuremberg” (1961). But it was in other showbiz arenas that she triumphed again. Her April 1961 concert performance at Carnegie Hall, turned into a 2-LP set on Capitol, spent 13 weeks at no. 1 and won four Grammy Awards including Album of the Year.

“This was the one place where she was really was at home in the world,” her longtime conductor Mort Lindsey once said of her stage appearances. Audiences identified with her struggles, Garland herself said: “They can hear the pain and the humor in my voice, and they associate with it.”

Says Feinstein: “She was unlike anybody else in the history of show business. Judy created this pandemonium in an audience, and it is captured almost perfectly on the Carnegie Hall recording. It is electrifying.”

Garland conquered TV, too, first with a CBS special in February 1962 that drew a 50 percent share of the viewing audience and was Emmy-nominated as program of the year. A weekly CBS series followed in 1963-64 and, while it was beset with creative troubles and (scheduled opposite the top-ranked “Bonanza” on NBC) ratings difficulties, is now considered one of the great variety shows of television history.

Her entire life was marred by health and financial issues not of her making. Studio doctors prescribed amphetamines and barbiturates to her from a young age, resulting in lifelong addiction struggles. Her marriage to gambler Sid Luft and financial mismanagement by others often left her broke and in need of the next gig to support her children (including her eldest daughter, the later Tony, Oscar and Emmy winner Liza Minnelli).

Yet, says Fricke, “she was as warm and funny and decent a human being as she could possibly be under the circumstances. As a performer, she quite possibly has never been equaled.”

She was married five times (including marriages to composer David Rose, director Vincente Minnelli and producer Luft) and died in London in June 1969 of an accidental overdose of barbiturates. She was just 47. As her “Oz” co-star Ray Bolger said at her funeral, “She just plain wore out.”

“There was tragedy in her life, but she did not think of herself as tragic,” says Feinstein, who recalled that both Lucille Ball and Carol Burnett thought that Garland was the funniest person they ever met. “How many entertainers are there of that period who were willing to be raw and reveal everything? She should be remembered, and celebrated, because great art is timeless.”

Variety put it this way on June 25, 1969, two days before her funeral: “Whether they remember her because she was Dorothy of Oz, Andy Hardy’s girlfriend, or a girl tramp to Fred Astaire’s boy tramp; whether they’re thinking back to the birth of a star, born in a trunk, or a tired little woman at the Nuremberg trials; whether they think of her as a talented troublemaker, always getting newspaper headlines because of her temperamental outbursts or skipping starry-eyed through a series of stormy marriages; or a tiny, talented mite knocking the hell out of ’em on the stage of the Palace — they’ll remember Judy Garland.”

The Garland centennial is being celebrated in many ways over the next few months. She is “star of the month” on TCM, which is airing 31 of her films on Fridays in June.

Feinstein’s “Get Happy: A Celebration of Judy Garland” including film footage, photos, even Garland home recordings, will be performed at the San Diego Symphony July 16, the Cincinnati Pops Nov. 10-13, with a “Judy and Friends” variation at the Pasadena Pops on Aug. 13.

Fricke will host a series of career-retrospective events June 9-12 at the Judy Garland Birthplace & Museum in her hometown of Grand Rapids, Minn. And “Get Happy! 100 Years of Judy Garland,” an exhibition of original Garland costumes, posters and memorabilia will be on display June 10-12 at the Wilshire-Ebell Theatre in Los Angeles — the same location where Garland was discovered by an MGM producer in 1934, leading to her auditions for the studio where she made some of her most memorable films.