Susan Foreman: the Original Companion

When Doctor Who first aired in November of 1963, audiences were introduced to now imfamous Doctor -- then played by William Hartnell -- a time travelling alien from the planet Gallifrey.
The showrunners felt that an audience surrogate was needed to interpret the Doctor's alienish jargon and behavior. Thus, the companion was born. The Doctor's first human companions were Ian Chesterton (William Russell) and Barbara Wright (Jacqueline Hill,) teachers at Coal Hill School. At the time of the first episode, the Doctor was also travelling with his grand-daughter, Susan Foreman (Carole Ann Ford.)
Susan attended Coal Hill School, and her advanced knowledge in science and history -- along with her forgetting that in 1963 England had yet to adopt a decimal currency -- drew the attention of her teachers, Ian and Barbara.
Susan was not originally intended to be the Doctor's grand-daughter. The familial link was suggested by writer. Anthony Coburn. According to producer Verity Lambert, "Coburn felt there was something not quite proper about an old man travelling around the galaxy with a young girl for a companion." 
The unaired pilot painted a different picture of the Doctor and Susan, with dialogue stating that they were from the 49th Century. She was conceptualized as a "fugitive from the Doctor's home planet," a princess named Suzanne that the Doctor had rescued during his travels.
During the pitch for the show, Carole Ann Ford was told that Susan was going to be "an Avengers-type girl – with all the kapow of that – plus she would have telepathic powers. She was going to be able to "fly the TARDIS" as well as her grandfather and have the most extraordinary wardrobe". However, the writers decided to make Susan more of an "ordinary" teenager, someone that the teen viewers could relate to.

Ford appeared in the entirety of the first series as well as the first two stories of the second series before departing the show. She later appeared in The Five Doctors anniversary serial and the Dimensions in Time charity special.

James Chapman, a media historian, felt that the way that Susan was written was the issue. "She was required to fill the role of the 'screamer' and often had little to do beyond looking pretty and frightened," he wrote. Carole Ann Ford shared these sentiments, occassionally finding Susan to be "pathetic" and was exasporated that her character was not allowed to augment. She also found the series to be "repetitive." Ford has since starred in several Big Finish audio dramas as Susan and has found that the character has since been more well developed.
The production team offered little information on Susan and her back story. Ford confessed that she and William Hartnell would get together and brainstorm backstories for their characters. In this way, they concluded that the Doctor had done "something to annoy the other Time Lords," which in turn caused the banishment of the Doctor and Susan from Gallifrey.
Ford ackowledged that it wasn't until the 1990s that it was speculated that Susan was not biologically related to the Doctor, yet in 2013, she revealed that during the production of The Five Doctors ​ in 1983, the producers were adamant that there be no mention of the Doctor and Susan's familial ties. She intimated that "They said, 'We don't really want people to perceive him as having had sex with someone, to father a child.' I just screamed with hysterical laughter and said, 'In that case, I'm not doing it.'" The script was then altered to allow mentions of the characters' relationship.
Susan has never been my favorite classic series companion. I found her to be weak and annoying -- I come from a family of strong women, so I have no patience for weak women -- but recently I have begun to go back and examine her impact on the show.

Susan was very much a product of the times. In the '60s, women were not allowed to be strong and independent; they were seen as fragile and needy. I believe that Carole did as well as she could with what she was given. There has been so much progress in women's rights in the 55 years since the show aired originally; I'd like to think that had Susan been introduced now, she'd have been as feisty and self sufficient as her modern successors such as Donna Noble and Amy Pond. If we hadn't had the damsels in distress like Susan and Victoria Waterfield, we would not appreciate the strong women companions we have today.
I do think that the Doctor travelling with another of his race was a brilliant idea. The only time that has happened since Susan was with Romana I and Romana II in the late '70s. Many fans are hoping for Susan to make an appearance on the new series. Whether she will or not remains to be seen, but Susan has been given a new lease on life in the Big Finish dramas.