Leann Rimes celebrated her 31st birthday in front of the Lincoln Memorial in Washington, D.C. on Wednesday (28Aug13). The country star belted out Amazing Grace as part of the celebrations marking the 50th anniversary of Martin Luther King's iconic "I have a dream..." civil rights speech. The Butler stars Forest Whitaker, Oprah Winfrey and Jamie Foxx also joined U.S. President Barack Obama, former leaders Bill Clinton and Jimmy Carter and politicians and civil rights icons at the festivities. Rimes took to Twitter.com following her performance and wrote, "Such an honor to have sung for our past 4 presidents since I was a baby. Beautiful day. Now it's bday (birthday) party time!!"