On a cold, snowy March 29 night in 1984, Baltimore Colts owner Robert Irsay, unhappy with their playing facility, packed up his football team and moved it to Indianapolis.

Little did he know that action would change the course of baseball.

Baltimore mayor and future governor of Maryland, William Schaefer, didn’t want to see another team leave, so he advocated a new baseball-only park to be built downtown.

Oriole Park at Camden Yards opened in 1992 and immediately changed the idea of what a baseball stadium should be. Now in its 20th season, Camden Yards is still marveled at and has served as the foundation for 21 new ballparks that have been built since Schaefer’s wish became reality.

The plan to build a baseball-only stadium in the heart of downtown interested urban planner Janet Marie Smith, who said the Orioles hired her to follow team president Larry Lucchino’s vision of the park. Smith worked with architects from HOK Sport to create what would become Camden Yards.

After years of bland, multipurpose stadiums used for baseball and football, Schaefer learned what Smith said many cities discovered after years of multipurpose stadiums.

“It wasn’t until after a decade or two of practice that I think teams began to see that making it a home for everyone made it a home for no one,” Smith said. “You couldn’t justify putting up your championship banners or having your mascot all over the place or any of the things that would give it a little personality.”

For nearly four decades before Camden Yards, round “cookie-cutter” stadiums replaced the cozy, intimate layouts of early-20th century ballparks that helped make baseball “America’s Pastime.”

The likes of New York’s Polo Grounds, Philadelphia’s Connie Mack Stadium, Pittsburgh’s Forbes Field and Cincinnati’s Palace of the Fans were replaced with Palaces of the Moneysaver — stadiums built for mainly economic reasons.

Orioles’ director of communications Greg Bader said he believes that Camden Yards helped bring back distinctness to the new homes of baseball.

“There’s something real about a baseball stadium — real grass, unique angles and being a part of an urban-neighborhood setting,” Bader said. “Those are things a lot of other sports can’t offer. When you can build a facility that represents that, I think it has proven to be successful.”

With that fact realized, the Orioles planned to build a stadium at an old train yard. The large B&O Warehouse at the site would act as the foundation for the new park’s design.

Ben Barnert, a senior principal at Populous (formerly HOK Sport), worked on the design of Camden Yards under the direction of Joe Spear. Barnert said much of the old-fashioned exterior was inspired by the warehouse. By keeping the 1,116-foot long building, those involved in designing the park believed it would be a “very special project.”

“It’s very similar to building a house on a cliff overlooking the ocean,” Barnert said. “Or the instant recognition you get from seeing the ivory at Wrigley or the Green Monster at Fenway. We knew people were going to affiliate the Orioles when they’d see the B&O Warehouse as the backdrop.”

Just as the 106-year-old warehouse marks a part of Baltimore history, the stadium has added bits of Oriole history since its opening on April 6, 1992.

Beyond the tall right field wall, bronze baseballs mark the spots where players’ home runs have landed on Eutaw Street. Two other homers are marked by orange seats in left and right-center field — one marking the spot where Cal Ripken Jr. hit his 278th home run, a record for shortstops, and the other marking Eddie Murray’s 500th long ball.

Bader said the Orioles will hear from unknowing fans who randomly draw those seats and are excited about their significance.

Baltimore fans’ appreciation for the team’s history is evident by the amount of No. 5 Brooks Robinson shirts seen in the stands or on those people walking along Eutaw Street, looking at the shops or restaurants in the warehouse.

Eutaw Street, which has become a fan-favorite, actually came to be as a desperate move, Smith said. She said the area stretching beyond the outfield from center to right field was created to make fans from Washington feel like they arrived the minute they got off the train.

“The fact it has been widely applauded and used for inspiration for other parks is just a wonderful, validating thing to have happened,” Smith said.

Eutaw Street is a favorite feature of 56-year-old Orioles fan Kevin Kane, who follows the Birds despite living in the Bronx and growing up with a father and brother who were Yankees fans.

With things to do other than just watching the game, Kane said Camden Yards makes him feel comfortable and he believes people can go to the park alone and still have an enjoyable time.

Many parks have since imitated Camden Yards by featuring entertainment areas, but Oriole Park remains a fan-favorite for its classic appearance and allure — making the park a fitting fixture in the heart of a town known as “Charm City.”

In attendance for the Orioles’ June 12 game against the Rays, Mike Wozniak said he was impressed with Camden Yards. After seeing 18 of the 30 major league parks, including many of the stadiums built since Oriole Park opened, Wozniak still saw the appeal of the park that brought back the classic design.

After growing up in Pittsburgh, Wozniak said the amount of seating behind home plate reminded him of Forbes Field.

And though Camden Yards invokes feelings of the past, Wozniak said the park is still in good shape as it hosts its 20th season of baseball.

“It looks like it’s brand new,” Wozniak said. “The stadium’s almost 20 years old, but it doesn’t look it. Other than the new building smell, it looks like it was just put up.”

Wozniak’s opinion was shared by several fans in attendance at the game, but it doesn’t mean the park hasn’t been touched since its opening in 1992. Bader said the Orioles replaced all of the seats during the last two years and added what they call “social-seating areas.”

With drink-rail seating and bistro tables facing the field, all members of a party can watch the game while socializing.

Similar features are present in many of the new stadiums, and Smith said that’s due to a change in the way fans watch a game. Scorecards have been replaced by smartphones, and fans no longer need to intently focus on the game, Smith said. This has led to “looser” seating, highlighted by the social areas.

The ability to create flexibility within the designs of a stadium is one of the typical requirements Barnert hears today. He said trends have put a focus on spectator amenities and a variety of seating types. Barnert said San Diego’s PETCO Park has “26 or 27 different neighborhoods,” or seating options.

“Clients want that kind of flexibility, to be able to offer a variety of product to their spectators,” he said.

The improved attraction of ballparks’ appearance and offering may be a contributor to increased popularity across the majors.

According to ballparksofbaseball.com, attendance rose from about 40 million in the mid-’80s to a high of 79,447,312 in 2007.

Though large amounts of home runs produced during the “steroid-era” are often credited for boosting attendance, Barnert said the attractiveness of the new ballparks may have played a role. Plus, it wasn’t a coincidence that home run figures rose as new, smaller parks were built.

The fact parks have shrunk is well-known by one of the clients represented by John Maroon’s PR firm.

Maroon, who worked as public relations director for the Orioles from 1995-99 before starting his own firm, said cookie-cutter stadiums were “damned caverns” compared to today’s fields.

He said veteran Jamie Moyer, whom Maroon represents, is the first to say many new parks are smaller and geared toward hitters.

The combination of better seating and more action offer fans more incentive to head out to the park, Barnert said.

“Any time you can get the spectator closer to the action, it’s going to seem more intimate and more dramatic,” Barnert said. “That made it more exciting for the fan, but it also made it more exciting for the players because they seemed to be real close to the fans.”

That trend began with the park nestled into downtown Baltimore — the field prided on history and literally built on history, as Babe Ruth’s father owned a pub where present-day center field is.

While designing the stadium, Smith said she never thought about the influence Camden Yards would have. Rather, she remained anxious because about one question she heard from the public: “How do we know this park’s going to last?”

Smith said the pressure she and the designers felt to please the fans was “enormous.”

“I think all of our efforts just went 150 percent to making it as good as we could for downtown Baltimore and Orioles’ fans,” she said.

After 20 successful years, it’s clear the park is withstanding the test of time, and the question is now how Camden Yards will be remembered by future generations. Will it have the same aura and mystique of Fenway Park or Wrigley Field?

Barnert believes Camden Yards will be remembered as the first urban ballpark — the one that brought baseball back into the cities and put an end to the multipurpose stadiums built around parking lots.

The impact of Camden Yards is seen in its comparative age to other ballparks, as it’s now the 22nd oldest stadium in the major leagues — meaning 21 new stadiums have been built since 1992. In the 20 years before Camden Yards there were seven built.

When Camden Yards opened, nearly every other ballpark suddenly became out-of-date, as the park reconnected the city, fans and team.

“We always use the phrase to describe Camden Yards as ‘the ballpark that has forever changed baseball,’” Bader said.

“It has greatly impacted the way the game is played, and the way cities and communities interact with their team.”