UPDATED 5/18/17
2000 – Mid-Michigan Bucks (PDL) 1:0 New England Revolution (MLS)
The Mid-Michigan Bucks have always been one of the lower division troublemakers of the US Open Cup, and this match against the New England Revolution at 
Foxboro Stadium helped build that reputation. Goalkeeper Eric Pogue was the early hero for the Bucks, saving a Shaker Asad penalty kick in the 7th minute to keep the game scoreless. The Bucks stayed with the Revolution for 90 minutes using a high-tempo style of play and eventually sent the sparse crowd of 1,857 Revolution fans home disappointed.
Three minutes into stoppage time, midfielder Chad Schomaker scored the winner on an assist from Boniventure Maruti. The win was the first time an amateur side defeated a Major League Soccer team. The Bucks, however, remain the only amateur club to upset an MLS team without the help of extra time or penalty kicks. Their Cup run would come to an end in the next round, when the Miami Fusion of MLS came to Saginaw, Mich., they needed a penalty kick shootout to eliminate the giant killers after a 3-3 draw in regulation.
2000 – Chicago Sockers (PDL) 0:0 Kansas City Wizards (MLS) (Chicago advances, 7-6 on PKs)
The Mid-Michigan Bucks weren’t the only team slaying MLS giants in the Second Round of the 2000 Open Cup. The Kansas City Wizards were leading Major League Soccer in points at the time of the match, but that didn’t matter to the PDL’s Chicago Sockers, who were the defending champions of the fourth division league. Adam Throop of the Sockers put in a spectacular performance, keeping a clean sheet for 105 minutes despite 23 shots from the Wizards. Both teams slugged though extra time scoreless as well, and the 3,140 on hand at Forest View Park in Chicago eagerly awaited the penalty kick session to decide the game. Throop came though again, saving Uche Okafor’s penalty to give Chicago the win.
The Sockers, like the Bucks, went on to put a scare into their next MLS opponents. In the Third Round, the Sockers took on the Chicago Fire and only a Josh Wolff goal in the 22nd minute seperated the two clubs in a rare Open Cup derby match.
2006- Dallas Roma FC (USASA – Region III) 1:0 Miami FC (USL-1)
Dallas Roma FC pulled off one of the biggest upsets in the Modern Era of the US Open Cup (1995-present), defeating the USL First Division’s Miami FC 1-0 in front of their home fans in Dallas. Roma scored the lone goal of the match early in the game, when Miami midfielder Zinho was called for a handball in the penalty area. John Waters stepped to the spot and converted the penalty for the 1-0 lead.
The Roma defense, led by goalkeeper Jessie Llamas, held World Cup winners Romario and Zinho in check all night, only allowing Miami to attack from the side, instead of up the middle. Roma head coach Michael Schell did not start three of his regulars for disciplinary reasons, making the 1-0 lead that much more remarkable. When he eventually brought in the likes of Patrick Shamu and Mark Rowland, Schell said the Miami players began to get frustrated.
“They (Miami) realized these guys were better then the ones they replaced”, Schell said. It was during this time that both Michael Erush and Fabian Sandoval were sent off, leaving Miami with just nine men to finish the game. Schell was also quick to point out that the visitors did not take his team lightly, as they constantly put pressure on Roma’s defense throughout the night.
The win marked the first time a USASA club had beaten a team from the USL First Division. Roma are also only the second USASA team since 1995 to advance to the Third Round of the US Open Cup. “I don’t think I’m going to go to sleep tonight!” said an ecstatic Schell after a post-match dinner with his team.
Other Second Round upsets
1997 – San Francisco Bay Seals (D3 Pro) 1:0 Seattle Sounders (A-League)
1998 – Orlando Nighthawks (D3 Pro) 2:1 Milwaukee Rampage (A-League)
1998 – Chicago Stingers (D3 Pro) 3:2 Hershey Wildcats (A-League)
1999 – Mid Michigan Bucks (PDL) 2:1 Minnesota Thunder (A-League)
1999 – Carolina Dynamo (D3 Pro) 2:0 Orange County Zodiac (A-League)
2000 – Richmond Kickers (A-League) 3:0 Colorado Rapids (MLS)
2001 – Connecticut Wolves (MLS) 3:2 Tampa Bay Mutiny (MLS)
2001 – Charleston Battery (A-League) 4:1 Metrostars (MLS)
2001 – Seattle Sounders Select (PDL) 3:2 Dallas Burn (MLS)
2001 – Pittsburgh Riverhounds (A-League) 3:0 Colorado Rapids (MLS)
2003 – Bavarian SC (USASA) 1:0 Reading Rage (PSL)
2006 – Michigan Bucks (PDL) 2:1 Cincinnati Kings (USL-2)
2006 – Des Moines Menace (PDL) 1:0 Minnesota Thunder (USL-1)
2006 – Carolina Dynamo (PDL) 1:0 Richmond Kickers (USL-2)
2008 – Cleveland City Stars (USL-2) 2:0 Minnesota Thunder (USL-1)
2009 – Ocean City Barons (PDL) 1:0 (AET) Real Maryland Monarchs (USL-2)
2012 – Michigan Bucks (PDL) 1:0 Pittsburgh Riverhounds (USL Pro)
2012 – Cal FC (USASA) 4:0 Wilmington Hammerheads (USL Pro)
2012 – Ventura County Fusion (PDL) 3:1 (AET) Los Angeles Blues (USL Pro)
2013 – Reading United (PDL) 1:0 Harrisburg City Islanders (USL Pro)
2013 – Ocean City Nor’easters (PDL) 1:0 Pittsburgh Riverhounds (USL Pro)
2013 – Des Moines Menace (PDL) 1:0 Minnesota United FC (NASL)
2013 – FC Tucson (PDL) 2:2 (4:3 PKs) San Antonio Scorpions (NASL)
2014 – Fresno Fuego (PDL) 2:0 Orange County Blues (USL Pro)
2014 – Chattanooga FC (NPSL) 3:1 Wilmington Hammerheads (USL Pro)
2017 – Reading United AC (PDL) 3:2 New York Cosmos (NASL)
2017 – Christos FC (USASA) 1:0 Richmond Kickers (USL)
2017 – Charlotte Eagles (PDL) 3:2 Charlotte Independence (USL)
2017 – Michigan Bucks (PDL) 1:0 Indy Eleven (NASL)
2017 – Chicago FC United (PDL) 3:1 Pittsburgh Riverhounds (USL)