The U.S. Green Building Council (USGBC) released their annual ranking of the Top 10 States for LEED this morning, with Illinois claiming the top slot for 2015. With a total of 161 LEED projects and 3.43 square feet of LEED-certified space per resident, the state of Illinois has retained the no. 1 position in the U.S. for the third consecutive year.

LEED, or Leadership in Energy & Environmental Design, is a green building certification program that recognizes best-in-class building strategies and practices. To receive LEED certification, building projects satisfy prerequisites and earn points to achieve different levels of certification, according to USGBC rules.

“LEED has become an essential tool for the transformation of building design and construction,” said Rick Fedrizzi, CEO and founding chair of USGBC. “By recognizing these states excelling in the use of LEED, we are celebrating the green building professionals, architects, business, policy and community leaders who work tirelessly to design and develop innovative solutions toward a healthier, more sustainable future.”

Within the top 10 states for LEED in 2015, a total of 1,633 commercial and institutional projects became LEED-certified, representing 274.9 million square feet of real estate altogether.

Compared to last year, the average LEED space per resident jumps to 2.47 square feet in 2015, breaking the 2014 record of 2.34. The ever-increasing per-capita LEED space has reflected the growing awareness and participation of green projects across the U.S. states.

Six states on the list also appeared on 2014's list, with Utah, Washington, Nevada, and Texas soaring to the top 10 from previously lower positions. It has been three years since Washington, Nevada, and Texas made the top 10, in 2012. The state of Utah is a complete newcomer to the list, indicating rapid growth in its local LEED development.

Please note that District of Columbia, with the highest LEED space per capita (19.3 square feet), was not included in the ranking, as it’s a federal territory rather than a state. Nevertheless, it’s indisputable that the Mid-Atlantic region, including Maryland (3.06 square feet), Virginia (1.63 square feet) and D.C., has done a remarkable job the past few years.

Debuted six years ago, the USGBC annually looks at U.S. Census data and certification records of green building projects and ranks all U.S. states according to the per-capita square feet of LEED certified space. Read the full release from the USGBC, and see BUILDER's previous coverage here.