The future of Sports Illustrated is unclear after the magazine's publisher announced plans to lay off most, if not all, of its staff on Friday following a terminated licensing deal. That means Sports Illustrated's coveted "Swimsuit Issue" is also in jeopardy.

What was originally created in 1964 to combat slow winter months when many sports were out of season – the first Super Bowl wasn't played until 1967 – SI's Swimsuit Issue has transformed into a cornerstone of pop culture that has spanned decades and catapulted hundreds of cover models to superstardom.

The most recent issue, published in 2023, featured lifestyle guru Martha Stewart on the cover, marking the oldest cover girl in the magazine's history, in addition to actress Megan Fox and singer Kim Petras.

"I'm going to be the oldest person ever I think on the cover of Sports Illustrated," Stewart said at the time. "I don't think about age very much but I thought that this is kind of historic and that I better look really good."

Here's everything to know about SI's Swimsuit Issue over the years:

SPORTS ILLUSTRATED: To lay off most staff, putting future in jeopardy after nearly 70 years

How did Sports Illustrated Swimsuit Issue start?

The Sports Illustrated Swimsuit Issue was invented by editor Andre Laguerre as a way to "help fill the void between Jan. 1 and spring training" during the quiet months in the sports calendar, according to the Sports Illustrated vault. He ran a travel story on Jan. 20, 1964, featuring model Babette March smiling in a white two-piece bikini, which became known as the inaugural issue.

Laguerre tapped fashion reporter Jule Campbell to create a multi-page swimwear feature the next year, asking her, "How would you like to go to some beautiful place and put a pretty girl on the cover?” Campbell catapulted SI's Swimsuit Issue into the popular mainstay that it is known as today. She did so with an unconventional formula. At a time where skinny was considered high-end and editorial, Campbell instead opted for "more natural kinds of women" and put them on the cover.

“I wanted them to look like real people that were beautiful... I think our audience related to that,” Campbell said in Michael MacCambridge's 1997 book, “The Franchise: A History of Sports Illustrated Magazine."

List of Sports Ilustrated Swimsuit Issue cover models

Sports Illustrated has published Swimsuit Issues for nearly six decades, featuring dozens of models. Here is every person who has appeared on the cover of the Swimsuit Issue:

• Babette March (1964)

• Sue Peterson (1965)

• Sunny Bippus (1966)

• Marilyn Tindall (1967)

• Turia Mau (1968)

• James Becker (1969)

• Cheryl Tiegs (1970, 1975, 1983) – Tiegs is the first repeat cover model

• Tannia Rubiano (1971)

• Sheila Roscoe (1972)

• Dayle Haddon (1973)

• Ann Simonton (1974)

• Yvonne and Yvette Sylvander (1976) – The Sylvander twins have the first ever multi-subject cover

• Lena Kansbod (1977)

• Maria Joao (1978)

• Christie Brinkley (1979, 1980, 1981) – Brinkley is the first three-time cover model and the first to appear in consecutive years

• Carol Alt (1982)

• Paulina Porizkova (1984, 1985)

• Elle Macpherson(1986, 1987, 1988, 1994, 2006) – Macpherson holds the record for most covers with five

• Kathy Ireland (1989, 1992, 1994)

• Judit Mascó (1990)

• Ashley Richardson (1991)

• Vendela Kirsebom (1993)

• Rachel Hunter (1994, 2006)

• Daniela Peštová (1995, 2000, 2006)

• Valeria Mazza (1996)

• Tyra Banks (1996, 1997, 2019) – Banks becomes the first African-American solo covergirl

• Heidi Klum (1998)

• Rebecca Romijn (1999, 2006)

• Elsa Benítez (2001, 2006)

• Yamila Diaz-Rahi (2002, 2006)

• Petra Němcová (2003)

• Veronika Vařeková (2004, 2006)

• Carolyn Murphy (2005, 2006)

• Beyoncé Knowles (2007) – Beyoncé is the first musician on the cover

• Marisa Miller (2008)

• Bar Refaeli (2009)

• Brooklyn Decker (2010)

• Irina Shayk (2011)

• Kate Upton (2012, 2013, 2017)

• Nina Agdal (2014)

• Lily Aldridge (2014)

• Chrissy Teigen (2014)

• Hannah Davis (2015)

• Ronda Rousey (2016) – Rousey is the first athlete cover model

• Ashley Graham (2016)

• Hailey Clauson (2016)

• Danielle Herrington (2018)

• Camille Kostek (2019)

• Alex Morgan (2019)

• Kate Bock (2020)

• Jasmine Sanders (2020)

• Olivia Culpo (2020)

• Megan Thee Stallion (2021) – Megan Thee Stallion is the first rapper cover model

• Naomi Osaka (2021) – Osaka is the first Black athlete cover model

• Leyna Bloom (2021) – Bloom is the first transgender cover model

• Kim Kardashian (2022)

• Ciara (2022)

• Maye Musk (2022)

• Yumi Nu (2022)

• Martha Stewart (2023) – Stewart becomes the oldest cover model at age 81

• Kim Petras (2023)

• Megan Fox (2023)

• Brooks Nader (2023)

Which athletes posed in SI Swimsuit Issue?

The SI Swimsuit Issue exclusively featured models in its early days, but the magazine opened its pages to athletes in 1997 with an appearance by German tennis star Steffi Graf. Russian tennis stars Anna Kournikova and Maria Sharapova and U.S. Women's National Team soccer star Alex Morgan appeared in an inset cover in 2004, 2006 and 2012, respectively, but UFC star Ronda Rousey was the first athlete to grace the cover of SI Swimsuit Issue.

Other athletes featured in the publication include tennis players Serena Williams, Venus Williams and Caroline Wozniacki; figure skater Ekaterina Gordeeva; race car driver Danica Patrick; and Olympians Amanda Beard (swimming, Jennie Finch (softball), Lindsey Vonn (alpine skiing), Lauren Jackson (basketball), Clair Bidez (snowboarding), Lacy Schnoor (freestyle skiing), Hannah Teter (snowboarding); and soccer players Megan Rapinoe, Crystal Dunn and Abby Dahlkemper.

Tennis star Naomi Osaka graced the cover in 2021, alongside rapper Megan Thee Stallion and modelLeyna Bloom, to become the first Black athlete cover girl.

"I wouldn't have thought that I would have been the first one," Osaka said during a sit-down with Tyra Banks, the first Black woman featured on the cover. "I'm glad that this barrier is being broken."

This article originally appeared on USA TODAY: Sports Illustrated Swimsuit Issue history from founding to cover girls