A rally on Thursday took US shares close to - or in some cases above - their levels of 10 September, before the suicide attacks on New York and Washington.
The Dow Jones Industrial Average has now recovered 85% of the 1,369 points it lost in the past four weeks, while the Nasdaq Composite and Standard & Poor's 500 indexes finished just above their pre-attack levels.
A strong week's performance in Asia saw Japanese shares also return to early September's prices, and the Nikkei 225 index gained almost 2.5% on Friday alone.
The London market achieved the same feat earlier in the week.
Tech stocks boost
The markets were spurred by a strong performance from computer chip and other technology stocks.
The high-tech dominated Nasdaq gained 75.22 points, or 4.63%, to close at 1,701.48.
The internet sector alone rose more than 8%, with strong performances from Yahoo, which gained $1.57 to $12.50 after an upbeat trading statement, and eBay.
Networking giant Cisco Systems rose $1.31 to $16.46, above its 11 September price.
The Dow, which includes 30 of America's biggest companies, gained 169 points at 9410.45.
Investors were in a buying mood as America remembered the victims of the 11 September attacks, one month on.
The world's biggest company, and a key Dow component, General Electric (GE) gained $1.03 to $38.94, after releasing third-quarter results that were in line with expectations.
Uncertainty
But there were mixed feelings about whether the rally would be sustained.
Charles G Crane, a strategist at Victory SBF Capital Management, said: "The fact that a company like GE was able to meet toned-down expectations is again the lack of a negative being a positive for the market.
"The sense I have is that we could retest the September lows before the end of the year or we could do it within next four or five trading sessions.
"We really don't know."
Share prices around the world plummetted in the wake of the 11 September but have been steadily recovering since.
London's FTSE 100 index of leading shares closed above 10 September's closing price of 5,033 for the first time on 5 October.