They're all good dogs–but some are also vital to their owner's wellbeing and independence.

Guide dogs are probably the best-known kind of assistance dog. They spend their careers aiding people with blindness to navigate the world safely and with dignity. The dogs might be seen assisting blind and visually-impaired people to navigate obstacles and safely negotiate traffic, helping them be more independent and mobile, writes Assistance Dogs International.

Their fore-puppers have been doing exactly the same thing for generations. Join us for the tail of guide dogs:

About 100 A.D.

Some people think that one of the murals of Herculaneum portrays a blind man with a guide dog. Author Michael Tucker made this suggestion in his 1984 book The Eyes that Lead: The Story of Guide Dogs for the Blind. Other images, like a thirteenth-century Chinese scroll painting, show people being guided by dogs, writes author Steve Swanbeck in The Seeing Eye.

Given the historically close relationship between people and dogs, it’s more than possible dogs have been helping blind humans for a very long time in some form or another.

1700s

It wasn’t until the eighteenth century that guide dogs became part of the medical establishment. Although images from the Middle Ages depict blind people relying on dogs, “the earliest systematic instruction of guide dogs” dates back to the mid 1700s, according to History.com. At a Paris hospital for the blind, people worked to train dogs who would help the patients.

1800s

Training guide dogs really took off in the 1800s, writes Swanbeck. “Textbook for Teaching the Blind, written in Austria by Fr. Johann Wilhelm Klein in 1819, notes that a rigid connection allows the person to feel when a dog is making a side movement or standing still, something that a soft leash cannot accomplish,” he writes. Klein, a teacher of the blind who pioneered methods of coping with blindness, preferred using poodles and shepherds as guide dogs. German shepherds are still a common guide dog choice.

Across the Atlantic, “there are several written accounts from the mid-1800s that talk about dogs helping to guide their blind masters,” he writes.

1900s

Dogs worked with humans on the front lines of World War I, delivering messages and tracking injured soldiers, writes historian Monika Baár. “This experience led to the emergence of a new human-canine alliance based on mutual trust,” she writes. “One manifestation of this intensified relationship was that guide dogs for the blind began to receive professional training during the war, first in Germany and later in several other countries.” Chemical weapons such as mustard gas blinded an unprecedented number of soldiers during the war, and they needed help. At the same time, she writes, the dogs could provide companionship in a difficult and lonely time. The role of dogs in the war also helped to create the idea of professional dog trainers who would train guide dogs going forward.

One of those dog trainers was an American woman named Dorothy Harrison Eustis. After visiting a German dog training clinic, particularly shepherds, she wrote a 1927 article for the Saturday Evening Post describing guide dogs as a way for blind people to find independence.

Eustis began training guide dogs and working with their owners. A blind man named Morris Frank visited her in Switzerland to be partnered with a guide dog, writes Steve Neumann for The Bark. Returning to the United States with a German Shepherd named “Buddy” at his side, Frank provided a vivid proof of how the guide dog improved his life. Buddy helped him to navigate across New York’s West Street, writes Neumann. “Known locally as ‘Death Avenue,’ it was one of the city’s most hazardous thoroughfares,” he writes. The pair did just fine.

With this proof in hand, Frank worked with Eustis to form The Seeing Eye, a guide dog training organization that helped make the working animals a common sight in the United States. It still operates today.