Give some stream of consciousness and then the answer. To comply with the new requirements and to manage the increased liability load, the organizers formed Black Rock City, LLC. Will Roger Peterson and Flynn Mauthe created the Department of Public Works (DPW) to build the "city" grid layout (a requirement so that emergency vehicles could be directed to an "address") designed by Rod Garrett, an architect. Rod continued as the city designer until his death, in 2011, at the age of 76. He is also credited with the design of all of the man bases from 2001 through 2012, the center camp cafe and first camp. With the success of the driving ban, having no vehicular incidents, 1998 saw a return to the Black Rock desert, along with a temporary perimeter fence. The event has remained there since.

Based on this passage, when did burning man move to black rock city?
The relevant information to answer the above question is: With the success of the driving ban, having no vehicular incidents, 1998 saw a return to the Black Rock desert, along with a temporary perimeter fence.
Therefore, the answer is 1998.