Have you ever wondered why the first person pronoun in English (I) is always written as a capital letter?
I was asked about this the other day and though I would investigate.
According to a blog post on Dictionary.com, it came about as a bit of an accident. In Old and Middle English the equivalent of I was ıc [iʧ], which was written uncapitalized. Its pronouncation changed over time and the c disappeared. On its own the ı looked weak, so scribes started writing it a bit taller, and by the 14th century is was typically capitalized.
According to a post on English Language & Usage, i was originally written without a dot as ı. It started to be written as slightly elongated when on its own or in Roman numerals when the last of several ı’s. This might have been to avoid confusion with punctuation marks, or with u, n or m.
A dot, or tittle, started to be used in manuscripts during the 11th century to distinguish i and j from other letters. Originally it was larger, but shrunk over time.
More information: http://blog.dictionary.com/tittle/