Here’s an image from last year (1861) that I missed. It is the policy of the Lincoln administration, and I would think, many Northerners agree with the sentiment given how many men have volunteered so far. As long ago as 1830 President Andrew Jackson said the Union must be preserved in a toast. Also in 1830 Daniel webster said “Liberty and Union, Now and Forever, One and Inseparable” in a speech.
As you can see, the Lincoln administration is following through on the Republican platform of 1861: