Messenger bags as we know them today were produced approximately in the 1950s. Globe Canvas/De Martini in New York produced them as bags for telephone linemen. The design of a messenger bag suited perfectly for the linemen, who were climbing telephone poles, since they could access it easily.
Single-strap shoulder bags, the ones that were used by messengers (this is from where the name messenger bag appeared), were designed. They were used by almost any type of messenger, whether it was Pony Express, postmen or bicycle messengers. A modern messenger bag finds its roots in the 1970s. At that time bicycle messenger companies purchased one color per company as identifiers of a sort. NYC was the sole bastion of messenger bags until the 1980s.
In 1989, two huge companies - San Francisco-based Timbuk2 (originally called ScumBags) and Toronto-based (now in British Columbia) Pac Designs - appeared. These famous companies are thought to be 'the forefront of the 3rd generation of a modern messenger bag.' They created their own interpretations of the DeMartini design - filtered through the lens of Manhattan Portage, Zo Bags and Courierware. Pac entered the prosperity of the highly-customized messenger bags in a bright way. It changed the very basic "big bag with a shoulder strap." Pac introduced messenger bags that converted from single to dual shoulder strap arrangements. Along with that, a whole spectrum of add-ons, pockets and subdividers was added.
A messenger bag started looking completely different in the 1990s, when a number of influential companies entered the stage. These were Bailey Works (Portsmouth), Push (Toronto), Chrome (Denver, now SF) and Roach (Vancouver - one of the first to introduce a 2-strap backpack-style bag). A tremendous amount of others from across North America, Europe, Australia and Japan tried to follow these giants. They develop numerous messenger bags - simple single-shoulder bags, super-custom shoulder or convertible bags, or dual-strap backpack-style bags - trying to satisfy the needs of every bicycle messenger.
Today, you can find a messenger bag for many walks of life from leather business cases from Victorinox to funky camera bags from Crumpler. Traditional messenger bag companies like Manhattan Portage and Timbuk2 continue to provide students and messengers alike with an interesting, still functional product. Everyone can update his image with a messenger bag and go to work or school in style.
Nowadays, a messenger style is used in many bags and by many designers and manufactures. Luxury paper bags, laptop bags, leather business cases, camera bags - almost all bags can be created in the messenger style. Most of them have more casual appearance and can be a great way to carry laptop or papers without broadcasting to everyone what you may have inside. Messenger bags are also widely used as promotional items to give to company's customers, staff or clients, and they can be very effective in achieving marketing goals.