Most scholars of Mexican American history mark César Chávez's unionizing efforts among Mexican and Mexican American farm laborers in California as the beginning of Chicano political activism in the 1960s. By 1965, Chávez's United Farm Workers Union gained international recognition by initiating a worldwide boycott of grapes in an effort to get growers in California to sign union contracts. The year 1965 also marks the birth of contemporary Chicano theater, for that is the year Luis Valdez approached Chávez about using theater to organize farm workers. Valdez and the members of the resulting Teatro Campesino are generally credited by scholars as having initiated the Chicano theater movement, a movement that would reach its apex in the 1970s.

In the fall of 1965, Valdez gathered a group of striking farm workers and asked them to talk about their working conditions. A former farm worker himself, Valdez was no stranger to the players in the daily drama that was fieldwork. He asked people to illustrate what happened on the picket lines, and the less timid in the audience delighted in acting out their ridicule of the strikebreakers. Using the farm workers' basic improvisations, Valdez guided the group toward the creation of what he termed "actos," skits or sketches whose roots scholars have traced to various sources that had influenced Valdez as a student and as a member of the San Francisco Mime Troupe. Expanding beyond the initial setting of flatbed-truck stages at the fields' edges, the acto became the quintessential form of Chicano theater in the 1960s. According to Valdez, the acto should suggest a solution to the problems exposed in the brief comic statement, and, as with any good political theater, it should satirize the opposition and inspire the audience to social action. Because actos were based on participants' personal experiences, they had palpable immediacy.

In her book El Teatro Campesino, Yolanda Broyles-González rightly criticizes theater historians for having tended to credit Valdez individually with inventing actos as a genre, as if the striking farm workers' improvisational talent had depended entirely on his vision and expertise for the form it took. She traces especially the actos' connections to a similar genre of informal, often satirical shows known as carpas that were performed in tents to mainly working-class audiences. Carpas had flourished earlier in the twentieth century in the border area of Mexico and the United States. Many participants in the formation of the Teatro no doubt had substantial cultural links to this tradition and likely adapted it to their improvisations. The early development of the Teatro Campesino was, in fact, a collective accomplishment; still, Valdez's artistic contribution was a crucial one, for the resulting actos were neither carpas nor theater in the European tradition of Valdez's academic training, but a distinctive genre with connections to both.