Here's a look at some notable birthdays being celebrated today:

Joni Mitchell
Age: 72
Occupation: Singer, Songwriter and Musician
Known For: Defining an era with iconic songs such as 'Big Yellow Taxi' and the gorgeous 'Woodstock,' having later success with jazz recordings, being called one of greatest songwriters ever by Rolling Stone, and having a strong influence on modern artists ranging from Stevie Nicks to Gwen Stefani

Lawrence O'Donnell
Age: 64
Occupation: Political Analyst, Writer and Television Personality
Known For: Hosting MSNBC's nightly political roundup 'The Last Word With Lawrence O'Donnell,' being a former staff director for the Senate Finance Committee, appearing as a political analyst on shows such as 'The McLaughlin Group,' and being an Emmy Award-winning producer and writer for the NBC political drama 'The West Wing'

Billy Graham

Occupation: Evangelist Preacher
Known For: Rising to celebrity status when his sermons were broadcast on radio and television, spending time with 12 U.S. presidents dating back to Harry S. Truman, and being number seven on Gallup's list of most-admired people of the 20th century

Johnny Rivers

Occupation: Singer, Songwriter and Producer
Known For: Late-1960s hits such as 'Seventh Son,' 'Poor Side of Town,' 'Summer Rain' and 'Secret Agent Man,' which enjoyed a resurrection when it was featured in the 1997 movie 'Austin Powers: International Man of Mystery'

Christopher Knight
Age: 58
Occupation: Actor and Reality-Show Personality
Known For: Playing middle brother Peter Brady on the hit 1970s sitcom 'The Brady Bunch,' a long post-TV career in the I.T. industry, and returning to television on the VH1 series 'My Fair Brady,' which profiled his eventual marriage to his now-estranged wife Adrianne Curry, who won the first cycle of 'America's Next Top Model'