The text on the poster says...
"UNCLE SAM'S YOUNGEST SON
Uncle Sam's youngest son was the Know Nothing Party's poster boy.
What eventually became known as the Know Nothing Party started off in 1845 as the Native American Party, losing Native from its name in 1855, to simply become the American Party.
Prior to 1860, with the election of the first Republican president, Abraham Lincoln, America had seen the coming and going of multiple political parties.
Since 1860 the American political system has been dominated by two parties, the Republicans and the Democrats.
To many observers the modern era version of the Republican Party has become a modern day version of the long gone Know Nothing Party.
The Know Nothing Party got what power it had by playing on the popular fear that America was being overwhelmed by immigrants.
Back then it was German and Irish Catholic immigrants which vexed the Know Nothings, while the modern era Know Nothings are vexed by what they call illegal immigrants, mostly from Mexico.
In 1849 a man in New York City, Charles B. Allen, started up a secret society to which members had to swear a secret oath. The secret society was called the Order of the Star Spangled Banner.
Fear of immigration, combined with being upset with Democrats, what with the Democratic leadership in many cities being Irish Catholics, had the members of the Order of the Star Spangled Banner campaigning to elect candidates in tune with their beliefs.
When out and about, and trying to influence voters, if a Star Spangled Banner campaigner was asked about his secret organization he was instructed to say, "I Know Nothing."
And thus the Know Nothing Party was born.
The modern era is not the first time some Americans have referred to some Republicans as Know Nothings.
In the 1890s Democrats frequently referred to Republicans as Know Nothings.
In 1892, during an election clash in Illinois between Republicans and Democrats, Democrat John Peter Altgeld memorably denounced the Republicans with words which manage to ring true today....
"The spirit which enacted the Alien and Sedition laws, the spirit which actuated the "Know Nothing" party, the spirit which is forever carping about the foreign-born citizen and trying to abridge his privileges, is too deeply seated in the party. The aristocratic and Know Nothing principle has been circulating in its system so long that it will require more than one somersault to shake the poison out of its bones."
Methinks it really is time for the Republican Party to go the way of the Whig Party, or for the Republican Party to find itself a leader who is willing to purge its Know Nothings and restore the Republican Party to being an entity worthy of being associated with Abraham Lincoln.
In the meantime, I am voting for Hillary Clinton next election cycle, unless someone better comes along....