In the 1970s, during the height of political corruption, Gangnam, the southern part of Seoul, is starting to be transformed into a developed area. Childhood friends Jong-dae and Yong-ki struggle to get by, until their shanty homes are demolished by local thugs. Desperate for cash, they get involved in violent political clashes, and are separated during one of the skirmishes. Three years later, Jong-dae lives as an adopted son of former gang leader Gil-soo and unknown to him a small-time gangster. Meanwhile, Yong-ki has raised as a made man inside Seoul's most powerful criminal organization, the Myeongdong-pa under Yang Ki-taek. Jong-dae meets foxy Min Seong-hee and is entangled in real estate business from tips Min Seong-hee gets from Park Seung-gu they enter into bigger business. Jong-dae finally meets Yong-ki and they together hatch plans to co-operate and become rich. Min Seong-hee introduces Jong-dae to a disgraced politician, Seo Tae-gon who still has political controls and they plan to raise him back to the political arena. They enter high-stakes battle going over land in Gangnam, by other political parties to fund secret presidential election and slush funds and drives up the plot-value of the city from inside information about future plan to turn Gangnam as an extended part of the capital. As the gangs fight over the rights to various plots and to maintain power structure, Yong-ki betrays his people and eliminates opposition with Jong-dae. Yong-ki who had to save his skin from suspicion of his boss kills Gil-soo. Jong-dae realizes this and keeps an eye on him. Meanwhile, Yong-ki's gang motivates him to overthrow Jong-dae and take over the whole operation when it is all over. After Seo Tae-gon's final mission they face each other and Jong-dae threatens Yong-ki to disappear and eliminates his gang members. Seo Tae-gon, to turn a new leaf in his career, recruits two new goons as his henchmen and puts them in charge to assassinate both Jong-dae and Yong-ki and they do so while Seo Tae-gon announces his nominee-ship for election and dances with Min Seong-hee. The ruling government declares its intent to adjoin Gagnam to its capital. After years an aged Seo Tae-gon addresses the developed city of Gangnam about his commitment to the city.
This was the final film in director-screenwriter Yoo Ha's "street series" trilogy, after Once Upon a Time in High School (2004) and A Dirty Carnival (2006). He called it "a story about people who are used, then discarded, about lives that are, like the buildings they live in, unauthorized. [...] represents the obsession over land ― land from which we are born, to which we return when we die. It is a feast of all things wretched."
Yoo originally didn't want to cast Lee Min-ho in the leading role, finding Lee's breakout performance in TV series Boys Over Flowers "a bit cheesy" and that the actor was "so handsome he was like a manhwa character." But after being convinced by his wife, Yoo realized the potentially huge impact of "flower boy" actors completely transforming their image, and together they collaborated to "burn to the ground" Lee's previous screen persona as a chaebol's son. Lee filmed a sex scene with actress Kim Ji-soo, but it was not included in the final cut because Yoo felt it was unnecessary to the flow of the film.
Yoo also asked actor Kim Rae-won to shed 15 kilograms since his character works as a rag man in the beginning of the film; Kim lost the weight in one month, which he said also made his fist-fighting scenes as a gangster more realistic.
Filming began on April 16, 2014 and wrapped on August 31, 2014.
The early Korean working title was Gangnam Blues (Hangul: 강남 블루스), which was changed to Gangnam 1970 in October 2014. Gangnam Blues was retained as the international English title.
Gangnam Blues was released in 684 theaters in South Korea on January 21, 2015. Despite its "restricted" rating, it topped the box office on its opening day, with 152,500 tickets sold. Within 5 days, it had reached the 1 million admission mark (1,097,103). After 35 days of release, the film recorded 2.19 million admissions.
An uncensored version (running time: 141 minutes) became available for streaming on VOD service IPTV on March 19, 2015.
The film was released with a different cut for the Chinese market in March 2015, in order to capitalize on Lee Min-ho's big fan base in the region. The new cut included more scenes of Lee, including those further developing the relationship between Lee's character and his love interest (played by Kim Ji-soo), as well as an alternate ending.
Modern Korean Cinema's Pierce Conran called the film "an evocative and immensely entertaining saga that pits a common tale of brotherhood and betrayal against a thrilling period setting mired in violence and corruption" and praised it as "one of the most beautifully designed and lushly filmed Korean productions ever made." He found Lee Min-ho "thoroughly convincing as a rising gangster with a cool exterior and emotional core," but that Kim Rae-won's performance had "a little less depth," yet nevertheless was Kim's best performance since 2006's Sunflower, in which he also played a gangster.
"Anak" by Freddie Aguilar was used in both Filipino and Korean Version of the 2015 for its trailer and actual feature.