The Vietnam War was still dragging on and the Minnesota Vikings had lost only one Super Bowl when the last passenger train rumbled out of Union Depot in downtown St. Paul. More than 40 years later, those trains are on the verge of making a comeback.

Shortly after 10 p.m. on May 7, the Empire Builder will jerk to a stop at Gate C outside Union Depot, marking the return of passenger train service to downtown St. Paul after 43 years and signaling the start of a new era for the historic train station that reopened in 2012 after an expensive and painstaking renovation.

Officials said that Amtrak’s Twin Cities operations will end that morning at the Transfer Road station in St. Paul’s Midway district, and move to Union Depot, joining five bus lines already providing transit service there.

Amtrak and Ramsey County will celebrate the new service on May 10, National Train Day, with a variety of free activities and exhibits at the Lowertown station.

“With Amtrak, the range of transportation options at Union Depot expands opportunities for travel connections throughout the Upper Midwest and beyond,” said Ramsey County Commissioner Rafael Ortega, who chairs the county’s rail authority, which owns the building.

Those options made Steve Gaschler, Philip Wells and Dick Wold smile Wednesday as they waited at the Transfer Road station for a shuttle. The three Midwesterners, just back after delivering new recreation vehicles to the West Coast, said the Union Depot will provide them with connections they don’t get at the current station.

“It should be a better deal, more convenient and probably less expensive,” said Wold, of Austin, Minn.

Officials first said they expected Amtrak would be pulling into the depot late last year. That date was pushed back to this winter and finally this spring, owing to delays in getting approval from freight lines operating the tracks and making the rail yard safe and secure for passenger stops.

But the deal has been done since November, when the county rail authority approved a 20-year lease with Amtrak that entitles the railroad to use Union Depot for ticketing, baggage, offices and a VIP lounge in the waiting area.

Amtrak will pay $144,586 in rent the first year, an amount that will grow by 3 percent each year for the term of the lease. It has the option to renew for another 20 years.

The new depot offers Amtrak riders a classic waiting room trimmed in gold and decorated with several pieces of public art. It will lack, however, one amenity offered at the old depot: free overnight parking.

Union Depot provides far more parking than the Transfer Road station, but it will cost travelers $5 to $20 per day (depending on the lot) to leave a car there during their train trip; hourly rates start at $4 to $6. That said, parking at Union Depot will get 24-hour security, and much of it will be sheltered.

For the most part, Amtrak ridership nationally and in the Twin Cities has risen in recent years. In its last fiscal year ending in September, nearly 31.6 million passengers used Amtrak, an annual record and the 10th increase in 11 years.

In the Twin Cities, nearly 117,000 passengers boarded or stepped off the Empire Builder, a 3 percent decrease from the year before. However, for the previous 15 years, Amtrak usage in the Twin Cities had risen by 19 percent. About 175,000 passengers used Amtrak in Minnesota last year.

Amtrak’s Empire Builder, named for the St. Paul rail tycoon who helped build the city’s first Union Depot — James J. Hill — provides service between Chicago and Seattle, including stops in Milwaukee and La Crosse, Wis.; Fargo, Grand Forks and Williston, N.D.; Whitefish, Mont., and Spokane, Wash.

Five bus lines also operate out of Union Depot: Metro Transit and Minnesota Valley Transit Authority, which provide local service, and Greyhound, Jefferson Lines and Megabus.

Metro Transit light rail will arrive at the depot June 14, when the Green Line begins operating between the downtowns of St. Paul and Minneapolis. The line has a station in front of Union Depot.

The federal government in 1971 launched Amtrak, a for-profit corporation partly funded with public dollars to provide intercity rail passenger service. After stopping the first few years in Minneapolis, Amtrak built a new Twin Cities station in 1978 in the Midway, near the border between the two cities.

Since at least 2000, St. Paul and Ramsey County officials have lobbied hard to move Amtrak to Union Depot, which had survived the end of train traffic to become a home for restaurants in the head house up front and a postal operations center in back.

In recent years, Amtrak officials have encouraged local efforts to restore and reopen historic depots across the country for passenger train service, such as Kansas City in 2002 and Denver this year.

Nothing could be done in St. Paul until 2005, when the Postal Service announced it was moving its Union Depot operations to Eagan.

In 2010, work began on a $243 million project — funded mostly by Ramsey County and the federal government — to restore the look and functionality of the 1920s-era depot. It reopened in late 2012.

Amtrak spokesman Marc Magliari said that the railroad will use the Transfer Road station as a base for some operational and mechanical work, and has no plans to sell it.