He launched the theatrical career of many actors, including James O'Neill, Mary Pickford, Lenore Ulric, and Barbara Stanwyck.

Belasco pioneered many innovative new forms of stage lighting and special effects in order to create realism and naturalism.

[3]: 13 [4] He began working as a youth in a San Francisco theater doing a variety of routine jobs, such as call boy, script copier, or as an extra in small parts.

"[3]: 14 From late 1873 to early 1874, he worked as an actor, director, and secretary at Piper's Opera House in Virginia City, Nevada, where he found "more reckless women and desperadoes to the square foot…than anywhere else in the world".

His developmental years as a supporting player in Virginia City colored his thoughts and eventually helped him to conceive realistic stage settings.

Among them were Leslie Carter, dubbed "The American Sarah Bernhardt,"[8] whose association with Belasco skyrocketed her to theatrical fame after her roles in Zaza (1898) and Madame Du Barry (1901).

[8] Other stars whose careers he helped launch included Jeanne Eagels, who would later achieve immortality as Sadie Thompson in Rain (1923), which played for 340 performances.

Both of these works were adapted as operas by Italian composer Giacomo Puccini (Madama Butterfly 1904—twice, after revision) and La fanciulla del West (1910).

Many prominent performers of the late 19th and early 20th centuries sought the opportunity to work with Belasco; among them were D. W. Griffith, Helen Hayes, Lillian Gish, Mary Pickford[8] and Cecil B.

After DeMille graduated from the American Academy of Dramatic Arts, he began his stage career under Belasco's guidance.

[11] DeMille's later methods of handling actors, using dramatic lighting and directing films, were modeled after Belasco's staging techniques.

The two remained in touch after Pickford began working in Hollywood; Belasco appeared with her in the 1914 film adaptation of A Good Little Devil.

[12][13] Belasco demanded a natural acting style, and to complement that, he developed stage settings with authentic lighting effects to enhance his plays.

[14]: 29 Belasco's contributions to modern stage and lighting techniques were originally not appreciated as much as those of his European counterparts, such as André Antoine and Constantin Stanislavski.

[3]: xi [14] America's earliest stage lighting manufacturer, Kliegl Brothers, began by serving the specialized needs of producers and directors such as Belasco and Florenz Ziegfeld.

[14]: 157  With regard to these modern lighting effects, Belasco is best remembered for his production of Girl of the Golden West (1905), with the play opening to a spectacular sunset that lasted five minutes before any dialogue started.

[14]: 29 Belasco became one of the first directors to eschew the use of traditional footlights in favor of lights concealed below floor level, thereby hidden from the audience.

[14]: 135 In his own theatres, the dressing rooms were equipped with lamps of several colors, allowing the performers to see how their makeup looked under different lighting conditions.

In his 1919 book The Theatre through Its Stage Door, Belasco relates the following incident: When I produced The Easiest Way I found myself in a dilemma.

So I went to the meanest theatrical lodging-house I could find in the Tenderloin district and bought the entire interior of one of its most dilapidated rooms—patched furniture, threadbare carpet, tarnished and broken gas fixtures, tumble-down cupboards, dingy doors and window-casings, and even the faded paper on the walls.

The basement of the Stuyvesant contained a working machine shop, where Belasco and his team experimented with lighting and other special effects.

The theatre, which was built by Morgan, Walls & Clements, opened in 1926, and was managed by Edward Belasco, another of David's brothers.