Who chose electors prior to 1820, and why did the process change?

In today’s election, people were given a chance to vote for their chosen political leaders. However, before 1820, the process is not the same. It was the State legislature who does the voting. Unlike today that president, vice president and any position in the government were specified to each political candidate, before; they did not have the same. Ones the lists is drawn from the ballot, whoever got the highest votes became to president, the second highest became the vice president and so on. If two people would have the same number of votes, then the house representative will choose between the two.