NEW YORK -- Wall Street is back in business.

Traffic is still snarled, streets flooded, subways out of commission and power out in many parts of Manhattan and beyond, but the New York Stock Exchange opened trading without a hitch Wednesday after a historic two-day shutdown caused by Superstorm Sandy.

At 9:30 a.m., right on schedule, New York City Mayor Michael Bloomberg rang the opening bell, then gave a hopeful thumbs-up. Cheers rose from traders on the trading floor below, falsely rumored to be flooded, but dry Wednesday morning, and festive.

"It's good for the city, good for country, it's good for everyone to get back to work," the mayor told CNBC moments later while leaving the exchange building at 11 Wall Street.

The stakes were high for trading to resume.

Wall Street traders and strategists were worried that a third day of delay would have meant more pent-up demand from customers to buy and sell stocks, resulting in a surge of orders that could send the market on wild ride. There were also doubts that there would be enough people in offices trading stocks for the market to match buyers and sellers smoothly.

But trading was placid from the start Wednesday, and much of the worry ebbed away.

"I've lived through a lot of events -- crashes, mini-crashes, events of mother nature, man-made events, terrible events like 9/11," said Ted Weisberg, president of Seaport Securities, 72, shortly after the opening bell. "Somehow or other the markets continue."

The last time the exchange closed for two consecutive days because of weather was during the Blizzard of 1888 - 124 years ago.

With power out in much of downtown Manhattan, the NYSE building Wednesday was an isolated hub of activity in a largely deserted and darkened neighborhood. The company that runs the exchange, NYSE Euronext, used backup generators to power its operations, including turning on the red, white and blue lights trained on its six-columned facade.

To Jonathan D. Corpina, a broker who made his way to the building by flashlight early in the morning, it was a welcome sight.

"Walking up this pitch-black street ... with the red, white and blue lights going, it was clear this was the only building in downtown Manhattan that was open," said Corpina, senior managing partner of Meridian Equity Partners. He added, referring to the opening: "It was important to have gotten that message out there that we are here, we are accepting orders, it's business as usual."

The opening followed days of scrambling by NYSE officials to make sure power, telecom connections and computers would be ready for a full trading day. The exchange organized car pools to get people to work, set aside special parking for those driving in and booked hotel rooms nearby for traders and other staffers. And it filled fuel tanks for its generators to the brim.

"We're not going to have power in lower Manhattan until probably the weekend, so we've got to make sure that our generator continues to be topped up," Larry Leibowitz, NYSE's chief operating officer, said from the exchange floor after the opening. "There's just lots and lots of details that we've spent the last 36 hours running through."

Leibowitz said that his biggest concern had been ensuring enough people who worked both at, and for, the exchange could make it into work. On Tuesday, NYSE ran a mock trading session with its all-electronic Arca trading system just in case too few people showed up.

In the end, more people made it in than the exchange had expected.

Many workers on the trading floor use the subway to get downtown, but that was not an option Wednesday. Hurricane Sandy flooded many tunnels, leaving the 108-year-old subway system with its worst damage in history. New York's governor, Andrew Cuomo, said says limited subway service will resume in New York City today.<co on Thursday>

"With subways down, I was wondering if people were even going to get to work today," said Randy Frederick, a managing director at Charles Schwab watching the opening from a TV at his Austin, Texas, office. "But obviously enough did. The markets opened stronger than many expected."

The two-day closing came just as big U.S. companies were reporting their quarterly earnings. That forced dozens of companies to postpone their reports to later this week, adding another wrinkle to the trading days ahead.

But trading volume Wednesday was normal, and it wound up being a relatively quiet day after all.

The Dow Jones industrial average gave up an early gain and wound up closing down just 10.75 points, at 13096.46. The Standard & Poor's 500 index edged down 0.22 point at 1412.16 and the Nasdaq composite lost 10.72 points to 2977.23.