A neat new NBER working paper by García-Jimeno and Robinson, somewhat misleadingly titled "The Myth of the Frontier" provides an empirical test of the "Turner Hypothesis" that the frontier was crucial in the development of American democracy and prosperity.
(Here is the NBER link. I cannot find an ungated link. Can anyone provide one?)
Here is what Turner said:
"These free lands promoted individualism, economic equality, freedom to rise,
democracy " Fredrick Jackson Turner
The paper takes 21 countries in the Americas, measures their frontier land share in 1850 and shows that both this variable and the number of constraints on the Executive in 1850 are both positive and significantly partially correlated with per capita income in 2007 and with the average democracy score (from Polity IV) from 1900-2007.
They then go on to add the product of the two variables to the specification, finding that the original two variables become insignificant while their interaction is positive and significant (and the r-squared rises). This is treated as evidence in favor of a "conditional frontier" thesis, where the frontier only helps if you have good institutions in place.
I must confess that I find interaction terms where one of the variables is not a dummy variable fairly bewildering (which is driving which? what about the induced colinearity?). So, I like the straightforward evidence (that the two variables are both significant in a multiple regression) a lot more than the interacted version, but the paper overall is well done and well worth reading, with a lot of historical information and examples of how the frontier was allocated across the Americas.