What were the original four federal holidays in the United States?

Context: The history of federal holidays in the United States dates back to June 28, 1870, when Congress created federal holidays "to correspond with similar laws of States around the District...and...in every State of the Union." Although at first applicable only to federal employees in the District of Columbia, Congress extended coverage in 1885 to all federal employees.

The original four holidays in 1870 were:

New Year's Day
Independence Day
Thanksgiving Day
Christmas Day

Answer: The original four federal holidays in the United States were New Year's Day, Independence Day, Thanksgiving Day, and Christmas Day.