JOLIET, Ill. — For the first time on a key Midwestern route between Chicago and St. Louis, an Amtrak passenger train topped 110 mph Friday, ripping through fog-shrouded farm fields and blowing past cars on a parallel highway.

The test run on a special train packed with journalists, politicians and transportation officials was a milestone in President Barack Obama’s vision of bringing high-speed rail to the United States and transforming the way Americans travel. It also was a welcome morale booster for high-speed rail advocates who have watched conservatives in Congress put the brakes on spending for fast train projects they view as expensive boondoggles.

“Four years ago we were nowhere. Illinois and the country was a wasteland when it came to high speed rail,” said U.S. Transportation Secretary Ray LaHood, among those celebrating onboard the train. “This is a dream come true today.”

The silver five-car, two-engine train held the high speeds for about five minutes along a 15-mile stretch of track between the central Illinois cities of Dwight and Pontiac before braking back below its usual top speed of 79 mph. Paying passengers on the route will start experiencing the faster speed on that short segment by Thanksgiving. Most of the route will get the higher speed by 2015.

The goal was to hit 110 mph, and for a moment the speedometer that officials were watching ticked up to 111. Illinois Gov. Pat Quinn pumped his fist in the air and gave a thumbs-up. He and the other dignitaries cheered, shook hands and congratulated one another.

Away from the celebrations, some rail and policy experts questioned whether the route could become profitable, pose serious competition to air and automobile travel, or ever reach speeds comparable to the bullet trains blasting across Europe and Asia at 150 mph and faster.

Kristina Rasmussen, vice president of the Illinois Policy Institute, said she thinks it’s very unlikely the route ever will make money. For one thing, she said, there will be political pressure to keep fares low, dimming prospects that Amtrak will take in enough to recoup maintenance and operating costs.

“We’re yoking ourselves to trains that will obligate taxpayers to provide billions of dollars in future subsidies,” she said.

Advocates say Midwest routes from Chicago hold the most immediate promise for high-speed rail expansion outside Amtrak’s existing, much faster Acela trains between Boston and Washington, D.C. They say it will give a growing Midwest population an alternative to rush-hour gridlock and overburdened airports, while promoting economic development along the route and creating manufacturing jobs.

In first announcing his plans in 2009, Obama said a mature high-speed rail network also would reduce demand for foreign oil and eliminate more than 6 billion pounds of carbon dioxide emissions a year — equivalent to removing 1 million cars from the roads. He set aside $8 billion in stimulus funds, directing the first round of money to speeding up existing lines like the one across Illinois and calling it a down payment on an ambitious plan to change the way Americans travel.

Even the short-term goals have run into trouble. Governors in Wisconsin, Ohio and Florida turned down hundreds of millions of dollars in stimulus funds, arguing not enough people would ride the trains and that states would be hit with too much of a financial burden for future operations.

Things could get worse for high-speed plans and for Amtrak if Mitt Romney wins the presidency next month. Romney and Republicans are calling for an end to $1.5 billion in yearly federal subsidies to money-losing Amtrak.

Nonetheless, proponents were cheered by Friday’s test ride.

LaHood said in an interview on the train that it was just the start of a decades-long endeavor to put in place “the next generation of transportation.”

“We have the safest aviation system in the world. We’ve got a great highway system and a great bridge system,” he said. “What we need to do is to provide transportation for the next generation.”

Amtrak ridership hit a record 30 million passengers nationwide last year — some of them pulled in by high gas prices, others by the convenience of not having to put down their electronic gadgets during a long journey.

“Driving is just wasting my time,” said Isaac Gaff, a 37-year-old music and arts director at a church who uses train time to plow through email on his laptop. He was waiting to get on the Amtrak line Thursday in Chicago to head home to Normal, in central Illinois.

As the infrastructure currently is laid out, there is virtually no chance trains will go much faster than 110 mph on the route, primarily because trains on Midwestern routes have to share the lines with the freight companies that own the tracks.

Work to upgrade the track began in 2010 and has included the installation of new premium rail and concrete ties as well as the realignment of curves to support higher speeds. Safer gates and new signals were installed at some highway crossings.

After another three years of upgrades, the $1.5 billion in improvements are expected to shave about an hour off the 284-mile journey between Chicago and St. Louis, which now takes about 5  1/2 hours. Future plans aim to shrink the time to under four hours.