All Philadelphia's major league teams enjoy large and famously demanding support, and the Union has needed little time to establish itself on the regional sports scene - thanks to smart management and the passion of the 'Sons of Ben' supporters group.
The group, named after Philadelphia's most famous citizen, Benjamin Franklin, pre-exist the club they support having played a key role, with their vocal demonstrations, of convincing MLS there was support for the game in the city.
PPL Park, on the banks of the Delaware River in Chester, Pennsylvania, will be packed on Sunday for the first leg of the Union's Eastern Conference semi-final against the Houston Dynamo.
"It is a big achievement for a club that is only two years old, we are so proud," Union CEO Nick Sakiewicz told Reuters on Thursday.
Reaching the post-season competition in the second year was an ambitious goal but one which Sakiewicz set as a target for Polish manager Peter Nowak and his players.
The post-season is by no means easy to reach, and has so far proved elusive for Toronto FC after five seasons in the league.
"We wanted to make the play-offs in our second year, we knew we had a good team last year but with all the challenges of launching a team and opening a new stadium, we knew it was going to be difficult in the first year," Sakiewicz said.
"We set the goal of doing it in the second year and we have achieved it - we don't take that for granted, there is still a lot of work in progress here."
The Union's purpose-built stadium holds only 18,500 and that has proved easy to fill. With season tickets sold out, the club is already looking at increasing the size of the venue.
"The way we designed the stadium was purposely to expand the stadium up to around 30,000 seats," said Sakiewicz, airing music to the ears of MLS management who have long argued that soccer-specific venues offer the best way forward for clubs.
But the Union have also made sure they embed themselves in their community and the club's branding - its logos, colours and name - all acknowledge the city's status as the 'Cradle of Liberty' and historic home of the Declaration of Independence - a move highly popular with the Sons of Ben supporters.
After their play-off berth was secured, the Union had one game left - at the rival New York Red Bulls - and their fans travelled there in numbers in loud and proud style.
"That gave us a taste of the play-offs, but also we got a taste on the field with a very fast and physical game," Nowak said. "Everyone is very excited to be here after 18 months.
Nowak's side includes the experienced and much-travelled Colombian keeper Faryd Mondragon and U.S. international forward Freddy Adu as well as exciting Congolese-American striker Danny Mwanga.
The Pole led D.C. United to the 2004 MLS title and he knows that when it comes to the knock-out world of play-off soccer, it is all about getting the basics right.
"It's not going to be about who plays the pr
Get the best features, fun and footballing frolics straight to your inbox every week.
Thank you for signing up to Four Four Two. You will receive a verification email shortly.
There was a problem. Please refresh the page and try again.