It has been a big week for Billboard-related milestones for women in music. Earlier this week, Taylor Swift became the first artist in two years to sell over a million copies of an album in its opening week (also giving her the best sales week since 2005 and making her only the second female artist to pull off that feat). Ke$ha has also managed to be a part of history this week, as her new single "We R Who We R" (from her upcoming second album Cannibal) debuted at number one on the Billboard Hot 100, marking only the 17th time that has happened in the history of the chart. It's especially impressive for Ke$ha, whose previous single "Take It Off" still sits at number 32.

Despite the fact that the Hot 100 has been around for the better part of six decades, debuts in the top spot didn't begin until 1995 when Michael Jackson's "You Are Not Alone" broke the dam and stormed the chart's top spot (that song, from Jackson's 1995 album HIStory, became the legendary Jackson's final chart-topper). Once Jackson set the bar, the deluge kicked in and three more songs debuted in the top spot in 1995: Mariah Carey's "Fantasy," Whitney Houston's "Exhale (Shoop Shoop)" and Carey and Boyz II Men's "One Sweet Day."

Ke$ha doesn't have the market cornered on recent number one debuts either, as there have been two in the past 12 months (Eminem's "Not Afraid" and Britney Spears' "3"). Along the way, an eclectic batch of artists like Aerosmith ("I Don't Want to Miss a Thing," 1998), Celine Dion ("My Heart Will Go On," 1997), Elton John ("Candle in the Wind 1997") and Diddy ("I'll Be Missing You," 1997). The number one debut has also been kind to "American Idol" contestants, as songs by Clay Aiken, Fantasia and Taylor Hicks all pulled off the feat.

Elsewhere on this week's Hot 100, Taylor Swift continues to make inroads, as digital sales of "Sparks Fly" and "Innocent" at numbers 17 and 27 ("Mine," meanwhile, still has a strong position at number 21). Swift has eight more songs on the chart, "The Story of Us" at number 41, "Dear John" at number 54, "Better Than Revenge" at number 56, "Haunted" at number 63, "Last Kiss" at number 71, "Enchanted" at number 75, "Never Grow Up" at number 84 and "Long Live" at number 85. (For those of you counting, that means that 11 of the album's 14 songs are currently in the Hot 100, and considering "Back to December," "Mean" and "Speak Now" all charted already, that means that every single Speak Now track has made an appearance on the chart -- a truly astounding feat made possible by the magic of digital download sales.)

The other big headline from this week is Willow Smith, who made a massive leap this week jumping from number 78 to number 11 with "Whip My Hair" (expect it to infiltrate the top five next week).