Prior to Powell's speech in Wyoming, the broad S&P 500 index had risen 0.4 percent, the technology-heavy Nasdaq composite index 0.2 and the Dow Jones industrial index 0.7 percent.
Then Powell opened the door ajar for a possible cut in the interest rate at the Fed meeting on September 17-18 - and it was received with open arms by Wall Street.
When trading closed, the S&P 500 had broken a five-day decline and risen 1.5 percent. The Nasdaq composite index and the Dow Jones industrial index had both climbed 1.9 percent.
Dow thus noted a record high closing level.
Increased probability
Prior to the speech, the market had priced in a 75 percent probability of a cut of a quarter percentage point in September. After the speech, it had risen to 91 percent, reports CNBC.
The bar is extremely high now for the Fed to leave interest rates unchanged, says Chris Zaccarelli, investment manager at the consulting firm Northlight Asset Management.
All of the very index-heavy so-called "magnificent seven" companies - Google owner Alphabet, e-commerce giant Amazon, iPhone manufacturer Apple, Facebook's parent company Meta, software company Microsoft, semiconductor giant Nvidia and electric car company Tesla - closed with gains after two heavy days.
Tesla surged as much as 6.2 percent.
State ownership in Intel
Processor manufacturer Intel has been negotiating with several investors for some time to receive a capital injection and has had a couple of heavy days behind it on the stock exchange.
But on Friday, the stock rose 5.5 percent.
Later in the evening, it became clear that the US state will receive a 10 percent ownership stake in the company in exchange for state funds for research, development and production of semiconductors.
During the week in general, the S&P 500 rose 0.3 percent, the Dow Jones industrial index 1.5 percent, while the Nasdaq composite index fell 0.6 percent.
