Apple CEO Tim Cook last week revealed that the company would be manufacturing a line of its Macs in the US next year, sparking speculation that the line in question could be the Mac Pro.

Cook announced Apple's plans to invest $100 million to move some of its Mac manufacturing to the US in 2013 during his first two in-depth interviews as CEO of the company, which were published on Thursday by NBC and Bloomberg Businessweek.

Fortune's Philip Elmer-DeWitt is convinced that the 'Made In USA' Mac line is the Mac Pro, and gives four reasons to back up this conclusion.

Read our round up of new Mac Pro rumours here

The first reason is based on labour economist at Michigan Manufacturing Technology Center Dan Luria's estimation that Apple's $100 million investment "sounds like a 200-job operation with about a million-unit output."

Elmer-DeWitt notes that Apple sold 18 million Macs last year, with only the Mac Pro and Mac mini selling less than a million per year, so Luria's estimation points to one of those two Mac lines, more likely the Mac Pro because it "is considerably heavier and more expensive to ship."

Second, Elmer-DeWitt reminds us that Tim Cook himself has already hinted that Apple will be launching a new Mac Pro next year, following comments from disappointed Apple users who were hoping that a new Mac to address the professional market would be announced at WWDC last June. 

In an email to an Apple user named Franz, Cook advised him not to worry, "as we're working on something really great for later next year."

Apple did update its Mac Pro at WWDC 2012, but was forced to remove its 'New' label from its online store after complaints that the only difference between the 'new' Mac Pro and its predecessor was a small speed boost. SEE: Mac Pro (mid 2012) review

The third reason Elmer-DeWitt believes Apple will manufacture the Mac Pro in the US next year is because the £2,000 to £3,000 computer will be able to absorb the costs associated with the move easier than the less expensive MacBook and iMac lines.

Finally, Elmer-DeWitt says that the Mac Pro is easier to build and customise than any other Apple product, so they could be a good starting point for manufacturing in the US.

During his interview, Cook explained that, while it might seem like an obvious option to move all of its manufacturing in the US, additional costs and lack of workers skilled in factory work would cause a problem.

Cook said that he hopes Apple's introduction of the Mac project in the US might encourage other companies to do the same.

Wall Street Journal reporter James R. Hagerty spoke with Willy Shih, Professor of management Practice at Harvard Business School about Apple's announcement, who said that he thinks we're "beginning to see a turn" in manufacturing.

"With labour costs rising rapidly in China and other emerging economies, many companies located here are thinking, "Wait a minute… I'm tired of the risk, and the inventory in the long supply chain, and the hard work of managing it. Labour arbitrage is over, the cost differential is not worth it"," he said.

Back in the 1990s, Apple manufactured its iMacs at its Elk Grove campus before moving its assembly lines to China, but the recent announcement that Apple will be returning some of its Mac production to the US has ignited excitement at the campus once more.

According to The Sacramento Bee, Elk Grove officials have been "contacting Apple to see if manufacturing might return to the Laguna Boulevard campus."

Apple already employees up to 1,800 workers in Elk Grove, whose jobs involve customer support, marketing and distribution.

An alternative could be a new Apple facility in Austin, Texas, reports say.

Forbes suggests that Apple's move to the US could change the way manufacturing and factory jobs are viewed in the country. "The opportunity to build Apples is bound to appeal to generations who own its phones, laptops and other devices."

See also:

Foxconn is exploring expanding its manufacturing in the US
A US Apple factory may be robot city
Top 10 tech predictions for 2013 from guru Mark Anderson
New iMac 2012 review round-up: what the critics say
New iMac 2012 21.5in review