Made up from 39 components and constructed via 80 separate factory floor steps, you'd be forgiven for thinking the subject in question is a piece of Nasa technology. This, however, is the drill dedicated to the creation of a pair of yellow, eight-hole Timberland boots. It's one of fashion's most recognisable pieces of footwear, favoured across the board, from hipsters to workmen, rappers and pop royalty. This boot, which gave Timberland its company name, celebrates its 40th anniversary this year and can truly be dubbed a fashion classic.

For a shoe to become so popular – and still sell millions of pairs each year – it must transcend fashion and penetrate another pop-cultural sphere. It's not enough to have a loyal following of fashionistas, you have to reach outside the industry bubble. Similar success has been achieved with the help of music or art by other labels, such as Converse – which had Hot Chip front its campaign in 2010, and currently has ads shot at gigs and in clubs around the world.

Often, though, this additional dimension isn't chosen by the brand, it happens organically; it's all about being in the right place at the right time with the right look, style and attitude. That's what Timberland did – and it shows in its earnings. Bought by sportswear giant VF Corporation in 2011, the brand saw net income increase by 13% in the first nine months of 2012, reaching £479m. You can be sure that the yellow boot accounted for a fair chunk of that.

Timberland treasures … the classic yellow boot, Earthkeepers boat shoe and Earthkeepers Cupsole boot

"It all began in the early 70s, when Sidney Swartz noticed that the American "working man" had a genuine need for durable leather boots that kept them dry while outdoors," says Chris Pawlus, Timberland's creative director. "So he made one, with the wheat-coloured waterproof leather … and it caught on pretty fast."

Defined by this yellow boot, the brand took off in the 1990s when US hip-hop artists wore Timberlands. Wu-Tang Clan, Mobb Deep and DMX wore the boots and gave them the all-important street cred. Producer and rapper Timbaland was even given his stage name – by Jodeci member DeVante Swing, according to his biography – due to his fondness for the boots.

Interest in the boot hasn't faltered among contemporary musicians; it's the footwear of choice for artists such as Rihanna, Jay-Z, Kanye West and A$AP Rocky. "I like the classic yellow boot as it's exactly just that, a normal no-frills boot," says Elgar Johnson, fashion editor at British style magazine i-D. "It's extremely masculine and incredibly versatile, it can be worn by 90s jungle heads and everyday builders. The boot is so popular because it doesn't conform to one certain genre, it can be put with anything and help create a look."

"The hip-hop community liked the authenticity of the yellow boot, it became a key part of their wardrobe," Pawlus explains. "We continue building gear so people can enjoy outdoor experiences while still looking good. They can also move into a more stylish space; you can wear the boots any place and with anything." As such, the wheat-coloured boot joins the likes of Converse Chuck Taylor, Nike Dunk and Clarks desert boot: effortless classics untainted by time.

Many of London's hottest menswear designers, including Martine Rose, Matthew Miller and Shaun Samson, have recently put Timberland back on to the catwalk in various customised incarnations. "It's all about function, that's what makes it an iconic piece of design. Every stitch, every piece of material and every step in the construction process. It works on so many levels, for everyone from rappers to riggers," says Matthew Miller.

Timberland was one of the first boot brands to advertise on television, and helped introduce the idea of putting logos – in its case, a tree symbol – on the outside of the footwear, hyping itself to create brand awareness. Now the brand is keen to put more emphasis on its green index.

Attention to detail … workers in the Timberland factory. Photograph: David Hellqvist

A growing area is its Earthkeepers line, Timberland's most eco-conscious footwear. It is designed for disassembly and at least 50% of the materials used can be recycled. The brand's commitment to nature also goes beyond the products; staff plant trees to replenish forests around the world. In China, Haiti and the Dominican Republic they've so far planted 2.5m trees. The purpose is not only to produce food, fuel and shelter but to help the 2,000 farmers involved on the Caribbean island to, according to the brand's website: "increase the productivity on their farmlands by more than 50%, thus resulting in increased income for their families." In China, the trees help to prevent sandstorms and desertification.

Made in an eight-plantation-strong factory outside Santiago in the Dominican Republic, the Earthkeepers boot is waterproof thanks to a midsole injection of thermo-plastic rubber. With more than 2,000 employees, the factory churns out a million boots and 500,000 boat shoes a year. Although there's a lot of heavy machinery, a surprising amount of the detailing is still done by hand.

"We are investing in automation but not to replace the workforce, simply to improve quality and consistency," says Alejandro Ordoñana, head of Timberland's Caribbean operations. "You cannot underestimate any of the jobs, but I think cutting the leather is our highest-skilled job. There are just some things you cannot change from a manual process. You could mechanise the cutting but you'd still need someone to spot defects like a scratch or a tick mark. The cutter makes sure that the particular piece is apt, so I guess that's the most detailed job we have, that and the hand-stitching of the boat shoe."

This attention to detail goes some way to explaining Timberland's enduring appeal.