What was the last state in the US to declare Christmas a national holiday, and in what year did this occur?

Oklahoma (1907)

Practically all the websites say 1907. See, for example:
http://www.factretriever.com/christmas-facts
http://www.didyouknow.cd/xmas/xmashistory.htm

But this one says 1890:
http://4thefirsttime.blogspot.com/2008/04/1890-last-state-makes-christmas-holiday.html

Oklahoma 1907

According to mac-2001.com/philo/crit/GREEK3.TXT -- Gradually during the middle and late 1800s, the celebration of Christmas became so popular, that it began to be declared a state holiday. Alabama was the first state to declare Christmas a legal holiday in 1836. By the time of the Civil War another twenty eight states had also instituted Christmas as a holiday. All U.S. states and territories recognized Christmas as a holiday by 1890. Federal employees were given Christmas as a paid holiday, beginning in 1885.

It was only during the mid 1800s that states in the US began making Christmas a legal holiday, with Oklahoma being the last state to do so in 1890 according to korrnet.org/reality/rc/1998_winter/editorial.htm

In 1836, Alabama became the first state to make Christmas a legal holiday. Other states followed suit; even Massachusetts legalized Christmas in 1856, almost 200 years after its ban. But the last state, Oklahoma, did not join in until 1907. So next Christmas, 2007, will be the centenary of Christmas being the first religious holiday whose celebration across the United States is sanctioned by law.

http://www.plaintruth.com/the_plain_truth/2010/12/when-christmas-was-illegal-in-america.html

In the United States of America, Oklahoma was the last to declare Christmas a legal holiday (1907).

http://www.didyouknow.cd/xmas/xmashistory.htm

The one that says 1890 would not be correct as Oklahoma didn't become a state until 1907.

http://www.50states.com/statehood.htm