Illinois, Maryland and Massachusetts led the U.S. Green Building Council’s (USGBC) 2015 top 10 states for LEED certification list. This includes states that exceed in sustainable building construction, design and transformation.

In 2015, Illinois had a total of 3.43 per capita certified gross square feet (gsf) and 161 total projects; Maryland had 3.06 per capita certified gsf and 127 total projects; and Massachusetts had 3.03 per capita certified gsf and 112 total projects. Illinois ranked No. 1 for the third year in a row. The only states that have made the list every year are Illinois and Colorado.

After the top three, the states include Washington, 2.60 per capita certified gsf and 101 total projects; Colorado, 2.43 per capita certified gsf, 95 projects; Nevada, 2.42 per capita certified gsf, 30 projects; California, 2.34 per capita certified gsf, 618 projects; Texas, 2.09 per capita certified gsf, 237 projects; Virginia, 1.63 per capita certified gsf, 121 projects; and Utah, 1.63 per capita certified gsf, 31 projects.

Rising from No. 5 in 2014 to No. 3 in 2015, Massachusetts was the most improved state. Utah made the list for the first time.

This list has the highest average—2.47 per capita space LEED-certified among the top 10 states—since 2010. The list, in its sixth year, is based on 2010 U.S. census data. It details certified commercial and institutional building projects from 2015 and is calculated using per capita figures to compare states with differences in population and number of buildings.

The most popular rating system among the top 10 states on the list last year was LEED for building operations and maintenance, which made up 49 percent of total square footage certified in 2015.

Though Washington, D.C., isn’t ranked, it continues to lead the nation with 19.3 square feet of LEED-certified space per resident last year. With Maryland and Virginia constantly on the list, the USGBC called the Mid-Atlantic the epicenter of green building.

California had the highest number of LEED projects and square feet. It also saw the most projects (three) that were LEED v4-certified. Colorado and Illinois had one LEED v4-certified project last year.