"As we know Slavery did not end in northern states, such as West Virginia, In part of the south occupied prior to January 1st 1863, and United States held Territories until the passage of the 13th Amendment to the United States Constitution. Would that be a more correct date?"

West Virginia adopted gradual emancipation with the Willy Amendment to the statehood bill that became law on June 20, 1863. However, on February 3, 1865, the governor approved an act abolishing slavery with immediate emancipation.

Slavery was abolished in U.S. Territories on June 19, 1862: "An Act to secure Freedom to all Persons within the Territories of the United States:
Be it enacted by the Senate and House of Representatives of the United States of America in Congress assembled, That from and after the passage of this act there shall be neither slavery nor involuntary servitude in any of the Territories of the United States now existing, or which may at any time hereafter be formed or acquired by the United States, otherwise than in punishment of crimes whereof the party shall have been duly convicted.
APPROVED, June 19, 1862."

"Juneteenth" refers to June 19, 1865 when news of the Emancipation Proclamation reached blacks in Galveston, Texas. The subsequent celebration has been observed for over 100 years and has been adopted as symbolic of the effective end of slavery in 29 states. As an aside, there is a commission in Missouri right now studying the issue of observing Juneteenth as Emancipation Day when actually Missouri abolished slavery in January 1865, a couple weeks before Congress finally passed the 13th Amendment.