The song's called "Sailing To Philadelphia", and it's on a Mark Knopfler CD of the same name. James Taylor guests on the one track.
It's a fine song on a fine CD.

Sailing To Philadelphia
by Mark Knopfler

I am Jeremiah Dixon
I am a Geordie boy
A glass of wine with you, sir
And the ladies I'll enjoy
All Durham and Northumberland
Is measured up by my own hand
It was my fate from birth
To make my mark upon the earth...

He calls me Charlie Mason
A stargazer am I
It seems that I was born
To chart the evening sky
They'd cut me out for baking bread
But I had other dreams instead
This baker's boy from the west country
Would join the Royal Society...

We are sailing to Philadelphia
A world away from the coaly Tyne
Sailing to Philadelphia
To draw the line
The Mason-Dixon line

Now you're a good surveyor Dixon
But I swear you'll make me mad
The West will kill us both
You gullible Geordie lad
Tou talk of liberty
How can America be free
A Geordie and a baker's boy
In the forests of the Iroquois...

Now hold your head up Mason
See America lies there
The morning tide has raised
The capes of Delaware
Come up and feel the sun
A new morning has begun
Another day will make it clear
Why your stars should guide us here...

We are sailing to Philadelphia
A world away from the coaly Tyne
Sailing to Philadelphia
To draw the line
The Mason-Dixon line