Shortly before Manchester United's visit to Eastlands for the 166th derby with their noisy neighbours City on Sunday, Wayne Rooney was asked if the Manchester rivalry was now the biggest in English football.

The England striker said it was not. "City have had their success recently, but I would probably say that United and Liverpool is still the biggest game," he said, via David McDonnell of the Daily Mirror. 

This answer was not given just because Rooney is a Merseyside lad who grew up a diehard Everton fan. It was not because the Red Devils consider City to be nouveau riche flash-in-the-pan contenders for the Premier League title. And it is almost certainly not because Rooney believed his side would be played off the park at the Etihad Stadium later that day.

It is because the rivalry between Manchester Utd and Liverpool is one of the oldest and fiercest in all of football. In fact, for football fans, it might just be one of the biggest rivalries in modern life, giving "cats vs. dogs" a run for its money.

So why do fans from the two cities located 30 miles apart hate each other so much more than a number of local derby opponents? The origins of the rivalry go back to the 19th century, and they have nothing to do with the football field...

The Rivalry Was Originally Economic

During the Industrial Revolution of the early 19th century, Manchester and Liverpool were both thriving economically. Manchester was known as "Cottonopolis" due to its abundance of textile factories (this is why Utd's kit had a gingham print last season). Liverpool, on the other hand, benefited from being a port city, with vast quantities of goods flowing in and out of its docks. 

Toward the end of that prosperous century, however, the Manchester Ship Canal was completed. This meant ships no longer had to dock in Liverpool—they could carry on up the Mersey all the way to Manchester via canal.

This trade route is why Utd and City both have ships on their crests, and it caused vast great resentment from the people of Liverpool, who lost potential income and jobs when the ships no longer stopped at the docks.  

The Rivalry Then Moved to the Pitch

So, why don't Liverpool fans begrudge City supporters too? And why don't Utd fans hold a grudge against Everton? The answer lies in both teams' history and heritage of success, and the fact that they each have a long-running expectation of winning trophies—often at the expense of one another.

New Premier League fans who have never seen Liverpool lift a league title may not appreciate it, but the Anfield side were a European powerhouse in the '70s and '80s, winning 11 league titles and four European Cups from 1972 to 1990. 

Manchester Utd succeeded Liverpool as England's biggest team in the early '90s, a role they have arguably retained since the present day.

Both clubs believe they are the greatest club in English football, and they have 121 major trophies between them to prove it. 

The football rivalry goes back to pre-war times, but a notable point in its 20th century history was the 1977 FA Cup Final. Liverpool had just won the league and were gunning for a treble at the European Cup Final with Borussia Moenchengladbach four days after the Wembley date. Utd denied Liverpool the treble with a hard-fought 2-1 victory. 

Utd were full of glee in 2010-11, when they won their 19th league title, finally surpassing the record 18-title haul of their Merseyside rivals. As they "welcome" Liverpool to Old Trafford for Wednesday evening's League Cup tie, they will be sure to remind their guests of the running tally. 

The Players Give No Quarter

Since Phil Chisnall moved from Utd to Liverpool in 1964, not a single player has transferred between these two clubs. To put that disdain in perspective, nine players have moved between Barcelona and Real Madrid since then.

In modern times, the rivalry has been intensified by the actions of certain players. Wayne Rooney was raised on the blue side of the Mersey and has made no secret of the fact that he grew up hating Liverpool. Former Utd captain Gary Neville also has had very few nice words to say about the Anfield side over the years, and his rivalry continues today in the Sky Sports studio with Jamie Carragher. 

In 2011, Luis Suarez made no friends at Old Trafford when he (allegedly) racially abused Patrice Evra, earning a ban and fine for his actions.

Fan Abuse Keep Escalating

Vitriolic insults and unpleasant incidents between fans of the two teams show no signs of abating. While acts of hooliganism have certainly decreased since the '80s, a small and very unpleasant contingent of Liverpool fans have mocked Manchester Utd with sick songs about the Munich Air Disaster that claimed the lives of eight players. Certain Utd fans have returned the ill-judged taunting with songs mocking the Hillsborough and Heysel tragedies.  

Fans have also been known to attack players. After the 1996 FA Cup Final—decided by a brilliant goal from Eric Cantona—one Liverpool fan spat at the Frenchman and another attempted to throw a punch at Sir Alex Ferguson. Additionally, Liverpool fans are banned from the entrance to the away end at Anfield after an egg was thrown at Ferguson during the '90s. 

Conclusion 

So, the uninitiated should now be prepared to witness a fierce football rivalry as Manchester Utd and Liverpool prepare to meet for the 187th time this Wednesday. It may only be the third round of the league cup, but this game will be fought like a cup final.

Expect to hear a particularly hostile welcome for Old Trafford foe Luis Suarez, who is set to play for Liverpool for the first time since biting Branislav Ivanovic last season.   

If you wish to learn more, you could do a lot worse than spending 26 minutes with this documentary...

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