The technology giant made it clear they were committed to San Francisco, and the city made clear it was committed to Twitter by offering tens of millions of dollars in tax breaks.
The move was intended to revitalize a blighted neighborhood that had not previously been gentrified.
It looks like the plan may slowly be working. The Tenderloin is still gritty, and overall rents are still lower than the rest of the city, but the place is changing.
We visited Twitter's HQ and walked the Tenderloin talking to those who seemed affected by it the most.