The nicknames "Motown" and "Motor City" have fallen by the wayside as Michigan's most populous city begins to earn a new reputation as a business hub. Home to six of the fastest-growing companies in America, Detroit is a thriving center for innovation in a vast range of fields, from education to energy.

For the 2015 Inc. 5000, we tracked the three-year growth rate for each company, comparing revenue from fiscal year 2011 with that of fiscal year 2014. Check out which company in "the D" grew the fastest.

6. Urban Science

Founded nearly four decades ago by engineer Jim Anderson, this software company provides retail performance consulting services, focusing on data collection and analysis. Growing nearly 44 percent since 2011 and earning more than $180 million in 2014, this is Urban Science's seventh time on the Inc. 5000.

5. Skidmore Studio

Ranked number 4,188 on this year's overall Inc. 5000, Skidmore Studio is a boutique creative agency specializing in connecting Millennials to existing brands like the arcade and restaurant chain Dave & Buster's and travel site Expedia. The company has been around since 1959, and in the past three years, it has achieved a greater than 66 percent growth rate, earning a 2014 revenue of $6.5 million.

4. FutureNet Group

This construction company provides innovative infrastructure services, mainly, to government agencies and large corporations. Founded in 1994 by CEO Perry Mehta, FutureNet Group has 179 employees and posted more than $8.5 million in revenue in 2014. Since 2011, the company has grown 155 percent, making it No. 2,427 on the overall list.

3. Walker-Miller Energy Services

Since its founding in 2000, this company has focused on decreasing energy consumption among its corporate and residential clients. Hitting No. 1,752 on Inc.'s list, Walker-Miller Energy Services specializes in distributing energy-efficient equipment to major utilities in the Detroit metro area. Last year, the company pulled in roughly $4.2 million in revenue, boasting a three-year growth rate of 229 percent.

2. The National Center for Faculty Development

Founded in 2010, this education company provides professional development services, training, and mentoring for more than 70,000 professors at 400 colleges and universities in the U.S. Headed by CEO Kerry Ann Rockquemore, the National Center for Faculty Development has grown its revenue to $2.9 million in 2014, up roughly 529 percent since 2011. That's helped the company land the 835th spot on this year's Inc. 5000

1. Merit-Hall

This fast-growing staffing company was founded in 2011 by Alex Riley and Patrick Beal, who wanted to address the persistent difficulty in finding staff for upcoming construction projects. Merit-Hall now supplies carpenters, general and demolition laborers, landscapers, and snow-removal personnel. With that pipeline--and nearly $6 million in annual revenue--the company handily hit No. 165 on the 2015 Inc. 5000. Overall, its sales have ticked up a whopping 2,400 percent since its founding.