For nearly three years, the trading floor of the Minneapolis Grain Exchange -- a glorious symbol of the city's storied past as a milling empire -- sat empty, its future uncertain.

The architectural gem had long been the place where trades were shouted for wheat, corn, oats and other commodities in a sunken pit on the exchange floor. But that raucous style of trading ended in 2008 after the exchange switched to an electronic system.

Over the summer, the business incubator CoCo, short for Coworking & Collaborative Space, opened on the trading floor, actually the fourth floor of the Grain Exchange's main building at 4th Street and 4th Avenue S. in downtown Minneapolis.

The old grain exchange had a new life. Then, almost two years to the day of its closure, it regained a little of the spotlight, when Google CEO Eric Schmidt visited the iconic space where corporate titans Pillsbury, Peavey and Cargill once trod. Schmidt discussed the virtues of the incubator concept in the new economy.

"Distance-working is a disaster," he said during his Dec. 6 visit to CoCo. "People want to work in a group. People are social."

It seems the trading floor's 20th-century splendor -- ornate columns, floor-to-ceiling windows and paintings depicting the city's milling past -- has made way for 21st-century entrepreneurism. So far, CoCo has about 48 members, ranging from individuals to small firms, many of them technology-oriented.

"It's epic," says CoCo's co-founder Kyle Coolbroth of the exchange building. "It's a place to come and think about great ideas."

The building's owner, MGEX, sought a tenant who was "very conscious of getting a new tenant that would appreciate and respect the space," said Rita Maloney, director of marketing and communications. "CoCo absolutely fit that requirement. We definitely did not want a cubicle farm in there."

The grand surroundings do hold a certain wow factor for visitors, but Coolbroth says its historical status presented some challenges in retrofitting the space for next-generation use. "It's not an easy space to do something with," he said. MGEX paid for the renovation, although Maloney would not reveal the pricetag.

While the floors were refinished, electrical service updated, data improvements installed and some '60s-era green steel desks removed, preservation rules prohibited any tampering with the interior walls. A small kitchen was added, and bathrooms remodeled in the hallway just off the trading floor. (The floor itself had only a men's room, a sign of the male-dominated commodities trade.)

Expansive wood tables where grain was once inspected by buyers were preserved. The former pit is still quite evident, although it is now home to several mid-century modern-style ottomans.

"This was, in many ways, the industry that built Minneapolis," said Dave Kenney, a Twin Cities author who wrote the 2006 book "The Grain Merchants: An Illustrated History of the Minneapolis Grain Exchange." "A lot of money is here because of it."

When the exchange was formed in 1881, it was originally known as the Minneapolis Chamber of Commerce, and it provided a market for Midwestern-grown grain. The operation moved to its current building in 1902, one of the first steel-encased structures in Minneapolis that helped usher in the skyscraper age. (Two other buildings were later attached on the north and east sides.)

Kenney says the exchange's founding fathers "obviously felt this had to be a special place and so it made sense to go fancy. They hired Minneapolis interior designer John Scott Bradstreet, who was quite well-known to the rich and famous, to fancify the whole space."

Enter Coolbroth and CoCo about 100 years later. Although the trading floor had been shuttered for nearly three years, Coolbroth says it was still "incredibly well-preserved. When we first walked in here it was as if time had stopped, people just got up and left. There were still trading cards on the windowsills." The main trading board still reflects the final trades of millet, flaxseed and hog bellies, among many other commodities.

CoCo now leases the rehabbed space (along with unlimited coffee) to individuals, small firms and groups. Workstations that can be rented part-time for as little as $50 a month, to corporate "campsites" leasing for $2,750 a month.

Coolbroth said it was the success of CoCo's St. Paul digs -- three floors of renovated warehouse space in St. Paul's Lowertown -- that led the incubator to search for more space across the river. All corners of the downtown and its periphery were considered -- from Elliot Park to northeast Minneapolis.

Minneapolis Mayor R.T. Rybak was especially interested in the fate of the exchange's trading floor, and served as a "huge supporter" of the incubator concept, said Cathy Polasky, director of Economic Policy and Development for the city.

Maloney of MGEX said the state of Minnesota and the U.S. Department of Interior extended tax credits for the trading floor's capital improvements, but declined to quantify them. The exchange also worked with utilities Xcel Energy and CenterPoint Energy to earn an Energy Star efficiency rating from the federal government for the trading floor.

Coolbroth says the space engenders big thoughts among members, who are encouraged to engage with one another, building off each others' skills and talents.

Kenney, author of the book on the Exchange, said he was delighted the trading floor attracted a new tenant, but also a bit amused, given the raucous nature of trading in the pit.

"When I first heard about it, I tried to imagine what some of the old traders would think," he said. "They were salt-of-the-earth types. Not too many people could have made a success in that very esoteric world of trade. I wonder what they would think of hipster entrepreneurs congregating in the space."

Janet Moore • 612-673-7752