| 100% | POPOV | 5 | Oleg —, Russian clown who in 1955 became the first to tour outside his home country |
| 34% | GIBB | 4 | Bobbi, who in 1966 became the first woman to run the entire Boston Marathon |
| 34% | ABLE | 4 | Monkey who became the first to return to Earth successfully in 1959 |
| 34% | WARRENGHARDING | 14 | U.S. president who, in 1922, became the first president to have his voice transmitted on the radio (3 wds.) |
| 33% | RICHARDBYRD | 11 | American explorer who in 1929 became the first person to fly over the South Pole: 2 wds. |
| 32% | LAIKA | 5 | Dog who became the first living being to orbit the Earth in 1957 |
| 32% | ORANGUTANS | 10 | In 2014 Argentina became the first country to recognize these primates' legal rights |
| 32% | PONCEDELEON | 11 | Explorer who in 1513 became the first European to set foot in 14-Across, and gave the state its name: 3 wds. |
| 31% | ELSTON | 6 | Howard who became the Yankees’ first Black player, in 1955 |
| 31% | ROALDAMUNDSEN | 13 | Norwegian explorer who in 1911 became the first person to reach the South Pole, one month ahead of 18-Across: 2 wds. |
| 30% | VALENTINA | 9 | ___ Tereshkova, cosmonaut who became the first woman to fly in space in 1964 |
| 30% | RAMIMALEK | 9 | Actor who became the first one of Egyptian heritage to win an Oscar for Best Actor in 2019: 2 wds. |
| 29% | LIUCIXIN | 8 | Author who, in 2015, became the first Asian to win the Hugo Award for Best Novel, for “The Three-Body Problem” |
| 29% | VINCECARTER | 11 | Atlanta Hawks forward who recently became the first to play in the NBA in four different decades: 2 wds. |
| 29% | DANICAPATRICK | 13 | Racing great who became the first woman driver to win an Indy car race in April 2008 (2 wds.) |
| 29% | ELMO | 4 | He became the first puppet to testify before Congress in 2002 |
| 29% | MANNYPACQUIAO | 13 | Filipino boxer who recently became the first person to hold a world title in four different decades: 2 wds. |
| 28% | KALPANA | 7 | ___ Chawla, American astronaut who became the first Indian woman to fly in space in 1997 |
| 28% | SALLY | 5 | ___ Ride, American astronaut who became the first American woman to fly in space in 1983 |
| 28% | THOMAS | 6 | With 65 Across, the first to see his name ''up in lights'' (1881) |
| 28% | HIJAB | 5 | Halima Aden became the first Sports Illustrated model to wear one in 2019 |
| 28% | LEONOV | 6 | Russian cosmonaut, the first to walk in space |
| 28% | EDEN | 4 | First home to humanity, in the Bible |
| 28% | MAE | 3 | ___ Jemison, American astronaut who became the first African-American woman to travel to space in 1992 |
| 28% | WHITSON | 7 | Peggy ___, American astronaut who became the first woman to command the International Space Station in 2007 |
| 28% | EILEEN | 6 | ___ Collins, American astronaut who became the first woman to command a space shuttle mission in 1999 |
| 28% | CZECH | 5 | Nationality of a poet and playwright who became the first president of his country |
| 28% | WOUK | 4 | Herman, who got his first publisher's contract serving onboard the USS Southard and went on to win the Pulitzer Prize in 1952 |
| 28% | MARIAHCAREY | 11 | "Fantasy" singer who recently became the first person to top the Billboard Hot 100 in four different decades: 2 wds. |
| 28% | GIRL | 4 | ___ Named Tom, musical group that became the first trio to win "The Voice" in 2021 |