Find Interactive Map Here: https://www.nytimes.com/interactive/2020/08/11/us/politics/vote-by-mail-us-states.html

From NYT website:

At least three-quarters of all American voters will be eligible to receive a ballot in the mail for the 2020 election — the most in U.S. history, according to a New York Times analysis. If recent election trends hold and turnout increases, as experts predict, roughly 80 million mail ballots will flood election offices this fall, more than double the number that were returned in 2016.

The rapid and seismic shift in how Americans will vote is because of the coronavirus pandemic. Concerns about the potential for virus transmission at polling places have forced many states to make adjustments on the fly that — despite President Trump’s protests — will make mail voting in America more accessible this fall than ever before.

“I have a hard time looking back at history and finding an election where there was this significant of a change to how elections are administered in this short a time period,” said Alex Padilla, the California secretary of state who chairs the Democratic Association of Secretaries of State.

Most of the changes are temporary and have been made administratively by state and local officials who have the power to make adjustments during emergencies like the pandemic.