Lyric discussion by FlairFan01 

Cover art for Taxi lyrics by Harry Chapin

According to interviews Chapin & his wife gave separately over the years, HC had taken a year off from his work as a documentary film maker to focus on growing his music career. A year later his career was non exsitant, he was now marred, raising his wife's 3 kids from her 1st marriage and she was pregnant with their 1st child, and he was having a hard time finding film work to make money, so applied for a cab drivers license, even though he didn't want to drive a cab (basically he needed to start making money again). He was depressed about the whole situation (his wife leaves a wealthy lawyer to marry him and he's an out of work film maker with a going nowhere music career who's broke, and they're about to have four kids!). Around this time HC heard that an Ex of his had married and was doing quite well, and thus the background for "Taxi" was born.

According to an interview his wife did with a songwriiters website a few years ago, "Sue" was based on an old college girlfriend, they never were in SF though and in fact other than one brief period before they married HC never worked outside the NY area. She stated she didn't know why SF was chosen as the site of the song and speculated it may have been simply because it fit the lyric better , it sounded better.

It made sense from a storytelling standpoint to continue the storyline in SF when he wrote "Sequel", the song that catches the two characters 10 years removed from this chance encounter, right before he passed away.

@FlairFan01 I like fact he wrote a sequel and it's as good as Taxi