Somerville is preparing a regional proposal for Amazon’s new headquarters that will also include sites in Cambridge and Boston, which will submit its own separate bid for the e-commerce giant’s new sprawling campus.

“We need to break out of our provincial and parochial mindset,” Somerville Mayor Joseph A. Curtatone said yesterday. “We’re not a region of vast land, our neighborhoods permeate across our city boundaries.”

Curtatone’s bid envisions an Amazon campus across as many as five cities, with large portions in Somerville’s Assembly Row and North Point, which reaches into Cambridge and Boston.

The bid also includes suggestions for North Station Tower, a planned office tower next to TD Garden, and a bus yard in Charlestown that is owned by the MBTA and the city of Boston.

Other sites include Union Square in Somerville and sections of Everett and Chelsea.

Somerville’s proposal is based on sites along the Orange Line that would satisfy Amazon’s call for 8 million square feet of space.

“A collection of sites located on the Orange Line can satisfy both the immediate need and the prospect of expansion over time by Amazon, as well as growth and expansion for the numerous partners and affiliates that will desire to be located near and adjacent to Amazon,” Somerville wrote in a summary of the proposal.

And although the Somerville pitch includes locations in Boston, Mayor Martin J. Walsh said that he is focused on his own bid, which is expected to focus on Suffolk Downs as a potential home for Amazon.

Supporters of the Suffolk Downs bid, including Speaker of the House Robert A. DeLeo and Revere Mayor Brian M. Arrigo, have said that they expect Amazon will be attracted to the prospect of a single site and single owner.

The emergence of the Somerville pitch means that Amazon will receive two different bids that include sites in Boston, along with a separate statewide bid that will advocate for Amazon to choose Massachusetts without suggesting a specific site.

In its request for proposals, Amazon has said it prefers a single submission for each region.

Gov. Charlie Baker said earlier this week that he expects between 10 and 20 bids to come from cities and towns across the Bay State.

“I don’t think any of us know what Amazon is looking for. The RFP was pretty clear though, with one bid,” Walsh said. “The state’s putting in a package, we’re putting in a package, Somerville’s putting in a package. I’m not sure who else is going to be putting in a package. We’ll see what happens.”