When I was in junior high school I did a report that traced back the party of the president, all the way back to Geo Washington. The names of the parties have changed a few times, but there has always been a conservative party and a liberal party. They trade back and forth, who's in power, throughout our history.
The funny thing I found was this. Republicans -- and the Republican lineage -- have not always been the conservatives. And Democrats and their predecessors weren't always the liberals. Sometimes they swapped, sometimes for years, sometimes for decades.
There has always been a dichotomy, a duality in politics but it's not always cut and dried. One party may favor conservative views on some issues but not others. The political landscape is always shifting, always shifting.
The Republicans freed the slaves. Democrats kept suffrage from passing for many years.