The history of Charles Schwab’s $22 billion purchase of TD Ameritrade extends back decades to when investing became more accessible for many Americans.

It got a big jump start on Sept. 26, 2019, when the brokerage industry’s move to zero trading commissions kicked into high gear — dramatically reshaping the short-term factors that ultimately led to the deal.

Check out this detailed timeline of the megadeal for the many developments that made it happen.