April 22 (UPI) -- On this date in history:
In 1500, Brazil was discovered by Pedro Alvarez Cabral.
In 1889, about 20,000 homesteaders massed along the border of the Oklahoma Territory, awaiting the signal to start the Oklahoma land rush.
In 1914, U.S. forces took control of the Mexican port city of Veracruz during the fighting of the Mexican Revolution.
In 1915, during World War I, German forces became the first to use poison gas on the Western Front during the Second Battle of Ypres.
In 1954, the Army-McCarthy hearings began in which Sen. Joseph McCarthy, R-Wis., accused the Army go going soft on communism, while the Army said it was pressured to give a speedy commission to a McCarthy aide.
In 1970, Earth Day was first observed.
In 1972, Apollo 16 astronauts John Young and Charles Duke walked and rode on the surface of the moon for 7 hours, 23 minutes. Young, whose career with NASA began in 1962, would spend the next four decades as an astronaut, retiring in 2004 at the age of 74.
In 1985, Jose Sarney was sworn in as Brazil's first civilian president in 21 years.
In 1992, more than 200 people died when a gas leak caused sewers in Guadalajara, Mexico, to explode.
In 1993, the Holocaust Memorial Museum was dedicated in Washington, D.C.
File Photo by Roger L. Wollenberg/UPI
In 1994, Richard Nixon, the 37th U.S. president and the only one to resign from the office, died four days after having a stroke. He was 81.
In 1997, a 126-day standoff at the Japanese Embassy in Lima ended after Peruvian commandos stormed the building and freed 72 hostages held by the Tupac Amaru Revolutionary Movement. All 14 rebels were killed.
In 2004, former NFL star Pat Tillman, who turned down a lucrative contract with the Arizona Cardinals to join the U.S. Army Rangers, was killed in Afghanistan. The U.S. military said later he was a victim of friendly fire.
In 2005, Zacarias Moussaoui, the only man charged in the United States in connection with the September 11, 2001, terror attacks, pleaded guilty and was sentenced to life in prison.
In 2006, Iraq's Parliament ratified the selection of Nouri al-Maliki as prime minister, ending a four-month political deadlock.
In 2016, world leaders from 175 countries gathered in New York on Earth Day to sign the Paris Agreement, the first international accord that outlines steps to combat climate change and lower carbon levels by 2100.
In 2019, the final film in the Marvel Cinematic Universe's Phase 3, Avengers: Endgame, premiered in Los Angeles.
Scarlett Johansson, Brie Larson attend 'Avengers' premiere
Cast member Scarlett Johansson (R) and boyfriend Colin Jost of "Saturday Night Live" attend the premiere. Johansson plays Natasha Romanoff/Black Widow in the film. Photo by Jim Ruymen/UPI
Brie Larson plays Carol Danvers/Captain Marvel in the film. Photo by Jim Ruymen/UPI
Cast member Robert Downey Jr. (R) and wife, producer Susan Downey attend the premiere. Downey Jr. plays Tony Stark/Iron Man in the film. Photo by Jim Ruymen/UPI
Downey Jr. (L) and cast member Bradley Cooper attend the premiere. Cooper voices Rocket in the film. Photo by Jim Ruymen/UPI
Chris Pratt (R) of "Guardians of the Galaxy" and fiance Katherine Schwarzenegger attend the premiere. Photo by Jim Ruymen/UPI
Chris Hemsworth (R) and wife, model Elsa Pataky attend the premiere. Hemsworth plays Thor in the film. Photo by Jim Ruymen/UPI
Liam Hemsworth (L) of "Isn't It Romantic" and wife, singer Miley Cyrus attend the premiere. Photo by Jim Ruymen/UPI
Benedict Cumberbatch (L) of "Doctor Strange" and wife, theater director Sophie Hunter attend the premiere. Photo by Jim Ruymen/UPI
Gwyneth Paltrow plays Pepper Potts in the film. Photo by Jim Ruymen/UPI
Cast member Don Cheadle (R) and girlfriend Bridgid Coulter attend the premiere. Cheadle plays James Rhodes/War Machine in the film. Photo by Jim Ruymen/UPI
Evangeline Lilly plays Hope van Dyne/The Wasp in the film. Photo by Jim Ruymen/UPI
Jeremy Renner plays Clint Barton/Hawkeye in the film. Photo by Jim Ruymen/UPI
Danai Gurira plays Okoye in the film. Photo by Jim Ruymen/UPI
Cast member Josh Brolin (L) and wife, model Kathryn Boyd attend the premiere. Brolin plays Thanos in the film. Photo by Jim Ruymen/UPI
Natalie Portman of "Thor" attends the premiere. Photo by Jim Ruymen/UPI
Linda Cardellini of "Avengers: Age of Ultron" attends the premiere. Photo by Jim Ruymen/UPI
Kevin Smith of "Behind the Scenes Jay and Silent Bob Strike Back" and daughter Harley Quinn Smith of "Yoga Hosers" attend the premiere. Photo by Jim Ruymen/UPI
Zoe Saldana of "Guardians of the Galaxy." Photo by Jim Ruymen/UPI
From left to right, LaMelo Ball, Liangelo Ball and Lonzo Ball of "Ball in the Family" attend the premiere. Photo by Jim Ruymen/UPI
Benedict Wong plays Wong in the film. Photo by Jim Ruymen/UPI