(CNN)Juneteenth is the oldest known US celebration of the end of slavery. African-Americans and others mark the anniversary much like the Fourth of July, with parties, picnics and gatherings with family and friends. Here's a look at Juneteenth, also called Emancipation Day, by the numbers:
By the Numbers: Juneteenth
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152 - Years since Maj. Gen. Gordon Granger (Union Army) first read the proclamation, General Orders, No. 3, in Galveston, Texas, notifying slaves of their emancipation, on June 19, 1865.
January 1, 1863 - Date President Abraham Lincoln issued the final Emancipation Proclamation, freeing those enslaved.
901 - Days in between the issuance of the Emancipation Proclamation and General Orders, No. 3.
13th - Amendment to the US Constitution that abolished slavery.
3,953,760 - Estimated number of slaves in the United States in 1860.
30.2 - Percentage of the population of Texas comprised of slaves, or "bondsmen," in 1860.
500,000 - Estimated number of free blacks in the United States in 1860. According to Encyclopedia Britannica, about half were in the North and half were in the South.
15 - States where it was legal to have slaves before the Civil War: Alabama, Arkansas, Delaware, Florida, Georgia, Kentucky, Louisiana, Maryland, Mississippi, Missouri, North Carolina, South Carolina, Tennessee, Texas and Virginia.
42 - States with laws or resolutions celebrating Juneteenth.
January 1, 1980 - Juneteenth became a state holiday in Texas, although it had been celebrated informally since 1865.
43,587,193 - African-Americans (one race alone or in combination) in the United States in 2015, according to the most recent Census Bureau estimate.
145 years - Age of the oldest Juneteenth celebration in the world, in Emancipation Park in Houston.
8 - Consecutive years during which Barack Obama, during his presidency, issued a statement to mark Juneteenth: 2009-2016.
40 - Congressional co-sponsors of House Resolution 268, Texas Rep. Sheila Jackson Lee's bill to "observe the historical significance of Juneteenth Independence Day," introduced in the House on June 17, 2013. It has been referred to the House Committee on Oversight and Government Reform.