What is Juneteenth and why do we celebrate it? Pictured: A Juneteenth celebration on June 19, 2004 in Richmond, California.  David Paul Morris/Getty Images

June 19 is an important day in history, known as Juneteenth. However, many people actually don't know just what the day celebrates.

For some people, Tuesday, June 19 is just another day on the calendar. However, for those who are direct descendants of former slaves, the day holds a much bigger significance, as it is the oldest known celebration to commemorate the ending of slavery in the United States.

According to Juneteenth.com, June 19, 1865, was the date that Union soldiers, led by Major General Gordon Granger, landed at Galveston, Texas and brought the news that the Civil War was officially over and those who had previously been enslaved were free men and women. The website notes how important it was in relation to President Abraham Lincoln's Emancipation Proclamation, which had actually become official two and a half years earlier, on Jan. 1 1863.

It was never really discovered why it took so long for slavery to officially end in Texas after the President's initial order.

Though slavery has been out of practice for over 150 years, Juneteenth is still a day that is celebrated among many who want to make sure the relevance of the day isn't forgotten. Several events will take place around the United States to commemorate the special day.

Among events taking place on Tuesday are:

The Dallas Juneteenth Festival: Taking place from 3-7 p.m. at the Martin Luther King Jr. Community Center, this free festival includes local craft and food vendors, fun and educational games for children, arts and crafts activities for the entire family and live entertainment by local artists, musicians, spoken word artists, and dancers.

Juneteenth in DC: From 5-8 p.m. at the African-American Civil War Museum, this event will feature a talk with historian C.R. Gibbs and a free Texas BBQ beginning at 5:30 p.m.

Other events will take place the following weekend as well. In Philadelphia, the third annual Juneteenth Musicfest and Parade will run with a series of events on Friday, June 22 and Saturday, June 23. The celebrations will continue on Sunday, June 24 with the second annual Freedom Day festival at the Please Touch Museum.