Joaquin Avila in 2009. (Ted. S. Warren/AP)

Joaquin Avila, a civil rights lawyer and activist who helped combat voting rights discrimination against Latinos and other minorities, including a successful effort to ensure greater political representation through census counts, died March 9 at his home in Shoreline, Wash. He was 69.

The Mexican American Legal Defense and Educational Fund, where Mr. Avila was president and general counsel from 1982 to 1985, announced his death and said the cause was cancer. After leaving the group, known as MALDEF, he spent years challenging laws to secure voting rights for minorities.

“Joaquin changed the political landscape of the United States and made it possible for Latinos to participate in electoral politics,” Antonia Hernandez, a former MALDEF president and general counsel, said in a statement.

Mr. Avila, a Mexican American who grew up in Compton, Calif., did his undergraduate work at Yale University, in a period when the Ivy League school was starting to scout far more vigorously for promising minority students. He then graduated from Harvard Law School before joining MALDEF, where as a young lawyer he said his goal was “to provide Hispanics with the necessary tools to compete effectively in society.”

He argued before the U.S. Supreme Court, and as he rose through MALDEF’s ranks, he worked on cases that expanded the civil and voting rights of Hispanics.

Over the years, the group was credited with helping increase the number of Spanish-speaking social workers in Los Angeles, Hispanic firefighters in Salinas, Calif., and Hispanic women working as electrician apprentices and border guards. MALDEF was instrumental in the 1982 Supreme Court case Plyler v. Doe, which struck down a Texas law that allowed the state’s school districts to ban undocumented immigrants from public school or to charge them tuition, thus guaranteeing those children a constitutional right to a free public education.

Mr. Avila was involved in more than 70 voting rights cases, MALDEF wrote in announcing his death. In 1980, his organization persuaded the U.S. Census Bureau to include a “Hispanic question” — marking a box to indicate Latino heritage — so that districts could be drawn to give the population political clout.

Two years later, the group helped broaden the scope of the landmark 1965 Voting Rights Act regarding the drawing of political districts. It was no longer necessary for plaintiffs to prove intent to discriminate for courts to mandate a redrawing.

“Prior to the amendment, the law discouraged us from pursuing litigation,” Mr. Avila told The Washington Post in 1983. “We just simply did not file.” The change, he added, “provided us with a very powerful tool.”

Mr. Avila went on to compare what he saw as systemic voting rights discrimination against Hispanics in Texas to the efforts to deny blacks the franchise in Mississippi. He called Texas “our Mississippi” in 1983, and MALDEF noted that he served as an attorney in a Texas district court case that deemed cities and school boards “political jurisdictions” under the Voting Rights Act of 1965.

In the late 1980s, Mr. Avila successfully argued that at-large elections in Watsonville, Calif., denied Latino residents proper political representation, spurring other California towns to follow, with more minority candidates being elected.

Mr. Avila later served as one of the attorneys in a federal voting rights lawsuit in which a federal judge ruled that the Los Angeles County Board of Supervisors excluded Hispanic constituents from representation by unconstitutionally gerrymandering the districts. The 1990 decision resulted in Los Angeles County’s first Hispanic-Latino majority district.

Mr. Avila also played a key role in creating the California Voting Rights Act, which passed in 2001, and continued to chip away at what he called the “blight of voting discrimination.” The act challenged at-large voting systems, which he said diluted the chances of minorities running successfully for office, especially at the local level.

His aggressive and lucrative filing of lawsuits against cities and school districts drew criticism, with the publication Education Week noting that many municipal officials described the law as “a boon for trial lawyers” and “akin to extortion.” Settlements for these types of cases were in the millions of dollars until attorney’s fees were capped at $30,000 by the state legislature in 2015.

“The question is whether having minority people on the board makes the elected body more sensitive to the particularized needs of the minority community,” Mr. Avila told Education Week in 2017. “I think that if you ask minority board members, they’ll probably say a resounding ‘yes,’ that it’s very important to be diverse and to have a voice at the table, and a vote at the table.”

Joaquin Guadalupe Avila was born Los Angeles on June 23, 1948, and grew up in Compton, Calif. He recalled that when he was a boy, his parents gave him a telescope and took him to a local planetarium, encouraging his education. He briefly began hanging out with street gangs and talked about leaving school, but his father stepped in.

“My dad, a foundry worker, was out of work at the time, due to an injury,” Mr. Avila recounted to the American Bar Association Journal. “He said, ‘You wanna end up like me? OK, drop out.’ ” He became class valedictorian and entered Yale, where he initially hoped to major in astrophysics. He said he felt unable to compete in that subject with prep-school-trained classmates and instead focused on political science.

After graduating in 1970, he went to Harvard and was an editor for the Harvard Civil Rights-Civil Liberties Law Review. Soon after receiving his law degree in 1973, he joined MALDEF, which had been formed only a few years earlier. He had worked in the group’s San Antonio office and, in 2015, reflected on seeing people who had been beaten up, fired or harassed when they advocated for rights in their communities.

“In many cases people were afraid to speak out, especially in smaller communities, because major employers would find out who the troublemakers were and they’d either immediately lose their jobs or be harassed,” Mr. Avila told the California Bar Journal decades later.

Mr. Avila’s most recent job was as a distinguished practitioner in residence and director of the National Voting Rights Advocacy Initiative at Seattle University’s law school. He was a 1996 recipient of a MacArthur fellowship “genius grant.”

Survivors include his wife of nearly 50 years, the former Sally Cabaruvias of Shoreline and Jurupa Valley, Calif.; three children, Joaquin Avila Jr. of Shoreline, Salvador Avila of Lynnwood, Wash., and Angelique Avila of Jurupa Valley; a brother; and four grandchildren.

In 2015, Mr. Avila told the Monterey County Weekly that he was still trying to get a state voting rights act passed in Washington state, Colorado, Arizona and Texas and that he had “a big agenda ahead of me.” In 1984, he said that when he started out he was not in the profession to make money but to effect social change.

“Change, as a result of our organization,” he told the ABA Journal in 1984. “That’s what is satisfying.”