Proto-Sinaitic — also called Proto-Canaanite — was probably the very first writing system that was purely phonetic, i.e. that did not use logograms. It did not include all the vowels (so is classified as an abjad and not an alphabet) but this still was a significant conceptual achievement.
Proto-Sinaitic is the ancestor of many (if not most) of the European and Asian writing systems, including the Latin script that I am currently typing. As such, Proto-Sinaitic must be counted as one of the most “successful” scripts ever.
The earliest examples of Proto-Sinaitic were found on the Sinai Peninsula in Modern Egypt, near some old turquoise mines that were worked in antiquity, presumably by slaves. The shape of the glyphs came from the shapes of some of the hieratic glyphs.
While this writing system was sound-oriented and not picture-oriented, there was still a slight connection between pictures and sounds. The glyphs represented the leading consonant in the name of that object the glyph looked like. For example, the word for “fence” was “heth”, and the glyph that looked like a fence represented the consonant “h”.
The words they got the sounds from were from the proto-Sinaitic words for objects, not the Egyptian words for the objects. For example, “beth” was the proto-Sinaitic word for “house” and “para” was the Egyptian word for “house”; the symbol that looked like a house represented the “b” sound, not the “p” sound.
NB: We don’t actually know which vowels went into “beth” and “para” because they didn’t write the vowels. Really, I should say that “b-th” and “p-r” were the words for “house”.