Charles Schwab Corp. is buying TD Ameritrade Holding Corp. in an all-stock agreement valued at $26 billion. 

The agreement brings together two of the pioneering direct investment platforms in the country, which have allowed millions of consumers to make direct online investments in stocks for more than 40 years. 

"We have long respected TD Ameritrade since our early days pioneering the discount brokerage industry, and as a fellow advocate for investors and independent investment advisors," Walt Bettinger, president and CEO of Schwab said in a press release. "Together we share a passion for breaking down barriers for investors and advisors through a combination of low cost, great service and technology."

TD Ameritrade is suspending its previously announced search for a CEO, naming Executive Vice President and CFO Stephen Boyle as interim CEO and president. Boyle will lead the company through its fiscal 2020 plan and the proposed integration with Schwab. 

"Partnering with Schwab on this transformative journey makes the right strategic and financial sense for TD Ameritrade," Boyle said in the release. "We share a common history — a journey since 1975 that made Wall Street more accessible and financial dreams more attainable for millions of Americans."

The combined firm will serve more than 24 million client accounts, $1.3 trillion in client assets and about $5 billion in annual revenue. Integration will take between 18-36 months and the firm will eventually move to Schwab's new campus in Westlake, Texas. Schwab, founded in San Francisco, will continue to have a presence there. 

The boards of both companies have approved the deal but regulatory approvals still need to take place. The transaction is expected to close by the second half of 2020.