The Declaration Over the Constitution

A post at the Edge of the American West describes the travels and displays of the Declaration of Independence and the Constitution.  In passing, this sentence struck me: "The Constitution does not seem to have been exhibited much until the twentieth century.)" The Declaration, and George Washington's commission, seem to have been displayed regularly.  I'm not sure what this means--were 19th century Americans more focused on the Revolution, independence from Britain, and less on the Constitution? Or were they more interested in life, liberty and the pursuit of happiness and less interested in separation of powers?