Of the 3 main causes of the war of 1812 (free seas, frontier pressure, War Hawks), which was the most significant? Explain your answer

The immediate causes of the War of 1812 were a series of economic sanctions taken by the British and French against the US as part of the Napoleonic Wars and American outrage at the British practice of impressment, especially after the Chesapeake incident of 1807.

In fact, the war had a far-reaching impact in the United States, as the Treaty of Ghent ended decades of bitter partisan infighting in government and ushered in the so-called "Era of Good Feelings."