After a single Monolith was sighted in Utah, many others started popping up:

From USA Today;

The saga of the mysterious monoliths – the tall, metal structures popping up and then vanishing around the world – shows no signs of stopping. 

 On Dec. 25, a monolith appeared at Corona Heights Park in San Francisco, except this time it was made out of gingerbread. It even came complete with icing and gumdrops. 

“We will leave it up until the cookie crumbles,” San Francisco Recreation and Parks Department General Manager Phil Ginsburg told KQED.

Another recent sighting: A 10-foot tall monolith appeared in a park in Ithaca, New York, according to the Ithaca Voice

There is some speculation that these monoliths sightings might be marketing ploy. While unconfirmed, it certainly feels like the kind of scheme Elon Musk has used in the past to garner interest in his various projects. The monoliths did appear around the time of a SpaceX rocket launch, and could easily be a part of promoting the company.