101,167,740 people cast votes before the polls opened on Election Day.
Prof. Michael McDonald at University of Florida has been compiling statistics on mail-in ballots and early in-person voting.
2020 General Election Early Vote Statistics
101,167,740 is more that all the ballots cast in the 1996 election when few states had early voting options. That number amounts to 73.4% of the total votes counted in the 2016 presidential and congressional election. The total number of votes cast could eventually reach 155,000,000.
In-person early ballots will be counted tonight with ballots cast on Election Day itself; the same technologies are used for early in-person voting and Election Day in-person voting. But mail-in ballots will take longer and will vary by state.
Poll closing times are not as critical this election because of mail-in ballots. But some states are able to count mail-in ballots more quickly than others. This site list all poll closing times in chronological order. Many states are listed twice because they are in more than one time zone. The nice thing about this table is that it converts closing times into all US time zones as well as UTC/GMT.
2020 Poll Closing Times for Statewide offices and Congress General Election Chronologically
CNN has a graphic which shows when each state begins processing mail-in ballots and when such ballots have to be received to be counted.
Mail-in ballots: When every state starts counting