Hillary Clinton became the first female presidential nominee of a major party on Tuesday night, a historic moment for any newspaper front page to document. But some front pages were missing a key component in their coverage of the event: a photo of Clinton herself.

Newspapers like the Chicago Tribune, the San Francisco Chronicle, the Houston Chronicle, and the Washington Post all ran headlines about Clinton's achievement, but accompanied them with photos of former president Bill Clinton, who spoke at the Democratic National Convention in Philadelphia Tuesday night.

The Wall Street Journal initially ran a photo of the former president but switched in later editions to a photo of Hillary Clinton speaking on a giant screen in the arena once one became available.

The omission of Clinton from these front pages stirred conversation on social media Wednesday morning. Was it a matter of selecting the best photo, of timing, or, as many observers argued, simply a case of sexism?

"Simple proof of enduring sexism: no Hillary, or even a woman, on the front page after 1st woman nominated president," tweeted Anne Helen Petersen, a features writer for BuzzFeed News. "This is akin to putting the person who announced the Oscar winner on the front page instead of the Oscar winner."

Petersen added, "Don't tell me they didn't have a picture of her. SHE IS THE FIRST FEMALE NOMINEE FOR PRESIDENT, YOU'VE GOT SOMETHING ON FILE."

simple proof of enduring sexism: no Hillary, or even a woman, on the front page after 1st woman nominated president pic.twitter.com/FvkxDfOAJK — Anne Helen Petersen (@annehelen) July 27, 2016

Others noted that both Clinton having not been at the convention in person and print deadlines could have been to blame, as Clinton's appearance on screen in the late hours after the former president's speech came after some deadlines and also made for a less striking photo than one of someone actually on the stage.

@moorehn To be fair, she didn't make an appearance until after many papers went to press. @WSJ put her on, but cd only make late editions. — Nikki Waller (@wallernikki) July 27, 2016

Related: Clinton nomination puts 'biggest crack' in glass ceiling

But for papers stuck without a good, relevant photo of Clinton at deadline, there were other options besides simply running a picture of her husband. Some newspapers, like The New York Times, went in a different direction and used photos of audience members at the convention cheering.

"Nominating conventions a little weird in being one of the few places where you win something major and not be there that night," tweeted Matt Pearce, the national reporter for the Los Angeles Times. "If I'm a photo editor I'm probably pulling my hair out last night."