The first "parties" were the Federalists and Anti-Federalists. These were not unified parties but they were the foundations of the current parties
Caucuses were replaced with party conventions in 1831 which was held by the Anti-Masonic Party. The first convention of major politics was by Anti-Jackson Republicans
The Whig Party collapsed and the Republicans under Lincoln came to power
After the Civil War those supporting the union were Republican and the confederacy were Democrats
1880s-1890s formation of independent parties, such as Populists and Greenbackers because of economic instability. These parties were not particularly strong and and Democrats adopted populist views and the Democrats overtook the independent parties.
In 1896 the separation of parties became more east west instead of north south with Republicans favoring industry and Democrats were small town farmers for low taxes
In California in 1910-1911 progressives and Governor Hiram Johnson were able to institute the direct primary -- citizens could use referendum voting to vote in legislature directly
There was a large shift from rural parties to more urban support of democrats in the 1930’s
In the 1960’s and 1970’s conventions of of both parties have changed. Delegates that were selected by party leaders are now chosen by primary elections and grassroots caucuses.
The South (from ‘72) has been more Republican and there has been an increase in Independent Parties
Political realignments happens sometimes because of issues that go across party lines and replace current issues - election of President Reagan was partially because people didn’t like Carter and his policies.
Split tickets were effective in 1988 when half of all House Democrats were elected by districts that had also voted for Republican President George Bush