Front Entrance Message
The lettering on the walls is not very clear to read, so I will state it for you.  The left message says, " We have lived long but this is the noblest work of our whole lives.  It will transform vast solitudes into thriving districts.  The United States take rank this day among the first powers of the Earth."  I'm not sure who wrote this.

The right message says, "The instruments which we have just signed will cause no tears to be shed.  They prepare ages of happiness forinnumerable generations of human creatures.  Robert Livingston May 3rd, 1803 after the signing of the treaty purchasing Louisiana from France."