John Parkinson, together with his various collaborators, may win top honors as the architect of many of LA's most famous and filmed noir icon buildings, but Claud Beelman runs a close second.
Beelman, born a Buckeye in 1883, had a career that lasted into his seventies. He died in LA in 1963. His architectural style evolved, over his long career, from classically inspired to iconic Art Deco, Streamline Moderne to mid-century modern.
Some highlights:

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The Talmadge (1922) A gift from Joseph M. Schenck to his wife, Norma Talmadge. 3278 Wilshire Blvd between Bullock's Wilshire and the Ambassador Hotel. If you need a unit with 4 bdms + maid's, they have one for you.

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Elks' Lodge No. 99 (1923-1924).On Park View St overlooking MacArthur Park. Heavily in demand as a film location.

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The Culver Hotel, Culver City (1924). Billed as Culver City's first skyscraper, the six story building, built on the site of Culver City's first movie theater, was owned by Harry Culver (founder of Culver City) and Charlie Chaplin. It is said that Chaplin lost his share of the hotel to John Wayne in a poker game. Housed the actors during the filming of the Wizard of Oz (and many other MGM films), including, of course, the little people. Has been used as a film location from the start.

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The Roosevelt Building (1926) Seventh & Flower, DTLA. Gives some weight and ominous glamour to the western part of downtown. Outstanding metalwork over the first-floor windows.

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The Heinsbergen Decorating Company Building (1928). On Beverly Blvd between Martel and Vista. Built for Anthony Heinsbergen (1894-1981) who ran his famous business here for 50 years. Dutch-born Heinsbergen contributed murals and other decorations to theaters, hotels, civic buildings etc across the country, including the Beverly-Wilshire, Hollywood Roosevelt, Elks' Lodge No. 99, The Wiltern Theater and City Hall here in LA. As part payment for his work at City Hall Heinsbergen accepted a load of salvaged bricks from old City Hall. They were used to build this slate-roofed, fantasy building. The stone trim includes statuary and gargoyles. The wall along the sidewalk between the doors encloses a koi pond.

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The Eastern Columbia Building (1930). Broadway at 9th. Beelman's universally-loved DTLA masterpiece is often used for location shoots.

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U.S. Post Office, Hollywood Station (1937).1615 Wilcox, between Selma and Hollywood Blvd. Anticipates the Thalberg Building (see below) right down to the plinth-mounted lanterns.

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The Thalberg Building (1938) at MGM (now Sony), Culver City. Louis B. Mayer ran his reign of terror and benevolence from his roost at the top. Thalberg died two years before completion. I sure miss the big "MGM" that used to sit on top of the cantilevered entrance cover. It was integral to the overall design.

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The Don Lee Mutual Broadcasting Building (1948) Vine Street at Fountain, Hollywood. Built specifically for television broadcasting with four large state-of the-art stages. CBS rented half the space. KCET was a tenant from 1964 to 1971. It is now the Academy of Motion Picture Arts and Sciences Pickford Center.

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The Harbor Building (1955). Wilshire at Irving. Built as Getty Oil Headquarters on the site of the old Getty mansion that served as a location for both "Sunset Boulevard" (1959) and "Rebel Without a Cause" (1955). Very similar in detail, materials and fenestration to Occidental Petroleum Headquarters at Wilshire and Westwood and the Standard Hotel (see below), originally built for Superior Oil. Another Getty Building, 3800 Wilshire (at Western) is also related.

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The Standard Hotel / Superior Oil Building (1956). Flower at Sixth, DTLA, directly across from the site of the Richfield Building. Completed when Beelman was 73. Shown to very good effect in the nod-to-noir "Kiss Kiss Bang Bang" (2005). Many of the Richfield Oil Company employees were stationed here while the Richfield Building was demolished in 1968 until they could move into the new Atlantic Richfield Company building at 5th and Flower in 1972. The Richfield Building was in very good condition when it came down. Charlie Jones, who retired as chairman when R.O. Anderson merged the company with Atlantic Refining, maintained it beautifully. Painters and other maintenance crews were still fulfilling work orders the day before the demolition crews arrived.
Below is another great shot lifted from a 2008
ethereal_reality post (thread page 5). It shows the Superior Oil Building/Standard Hotel going up directly across from the Richfield Building in 1956. Intersection of 6th & Flower looking east down 6th.

USC digital archive.