Tuesday marks the 150th anniversary of President Abraham Lincoln's landmark Gettysburg Address, which honored the lives lost in the bloody Civil War battle and came to symbolize democratic American freedom. 

Today, Civil War historian James McPherson and U.S. Interior Secretary Sally Jewell are scheduled to speak to mark the 150th anniversary of the seminal speech at the free Dedication Day event in Gettysburg, Pa. Pennsylvania Gov. Tom Corbett will also address the crowd, according to The Associated Press.

The event is held annually at Soldiers National Cemetery. Last year's commemoration drew around 9,000 people. This year's crowd may be even bigger due to the momentous anniversary event. 

The event marks the end of a year celebrating the Gettysburg Address for the park, city and college that share the name Gettysburg. Hundreds of thousands of visitors have come to the town to witness historical re-enactments and ceremonies. 

The Gettysburg Address was delivered almost five months after the battle, which left tens of thousands of men wounded, dead or missing. The address will be read by a re-enactor to mark the speech's anniversary.

The ceremony will begin in the morning with a wreath-laying at the Soldiers' National Cemetery. There will then be a graveside salute to U.S. Colored Troops at noon, then a tree planting ceremony later in the afternoon. 

The short address was not immediately considered a crowning oratory achievement. The Patriot-News in Harrisburg recently retracted a critical editorial of the speech published by its Civil War-era predecessor publication, The Harrisburg Patriot & Union. The newspaper says it now regrets not recognizing the speech's "momentous importance, timeless eloquence and lasting significance."

President Barack Obama declined an invitation to the event. Park officials say that Rutherford B. Hayes was the last sitting president to attend the event on Nov. 19 in Gettysburg. 

There are other events being held this week in Gettysburg, such as the "Gettysburg Address Gallery" at the park museum and visitor center. The exhibit features pages with signatures of people who attended the 1830 Dedication Ceremony, and a letter and signed pardon from President Lincoln. 

The annual Remembrance Day Parade will be held in the town on Saturday, featuring Union and Confederate re-enactors who will lay wreaths at the parts of the field where their units fought. 

The National Park Service is streaming Tuesday's ceremony live to 90,000 colleges, libraries, schools and museums across the country. 

There are five known copies of the original speech. The one that became the most famous is the version named after Col. Alexander Bliss, according to ABC News. 

Here is the full text of the famous speech: 

"Four score and seven years ago our fathers brought forth on this continent, a new nation, conceived in Liberty, and dedicated to the proposition that all men are created equal.

Now we are engaged in a great civil war, testing whether that nation, or any nation so conceived and so dedicated, can long endure. We are met on a great battle-field of that war. We have come to dedicate a portion of that field, as a final resting place for those who here gave their lives that that nation might live. It is altogether fitting and proper that we should do this.

But, in a larger sense, we can not dedicate -- we can not consecrate -- we can not hallow -- this ground. The brave men, living and dead, who struggled here, have consecrated it, far above our poor power to add or detract.

The world will little note, nor long remember what we say here, but it can never forget what they did here. It is for us the living, rather, to be dedicated here to the unfinished work which they who fought here have thus far so nobly advanced. It is rather for us to be here dedicated to the great task remaining before us -- that from these honored dead we take increased devotion to that cause for which they gave the last full measure of devotion -- that we here highly resolve that these dead shall not have died in vain -- that this nation, under God, shall have a new birth of freedom -- and that government of the people, by the people, for the people, shall not perish from the earth." -- Abraham Lincoln