Three years into Donald Trump’s presidency, the U.S. government is ramping up its efforts to seize private land in Texas to build a border wall.

Trump’s signature campaign promise has consistently faced political, legal, and environmental obstacles in Texas, which has the largest section of the U.S.-Mexico border, most of it without fencing. And much of the land along the Rio Grande, the river that forms the border in Texas, is privately held and environmentally sensitive.

Almost no land has been taken so far. But Department of Justice lawyers have filed three lawsuits this month seeking to take property from landowners. On Tuesday, lawyers moved to seize land in one case immediately before a scheduled court hearing in February.

The agency says it’s ready to file many more petitions to take private land in the coming weeks. While progress has lagged, the process of taking land under eminent domain is weighted heavily in the government’s favor.

The U.S. government has built about 90 miles (145 kilometers) of walls since Trump took office, almost all of it replacing old fencing. Reaching Trump’s oft-stated goal of 500 miles (800 kilometers) by the end of 2020 will almost certainly require stepping up progress in Texas.

Opponents have lobbied Congress to limit funding and prevent construction in areas like the Santa Ana National Wildlife Refuge, an important sanctuary for several endangered species of jaguars, birds, and other animals, as well as the nonprofit National Butterfly Center and a historic Catholic chapel. They have also filed several lawsuits. A federal judge this month prevented the government from building with money redirected to the wall under Trump’s declaration of a national emergency earlier this year. Also, two judges recently ordered a private, pro-Trump fundraising group to stop building its own wall near the Rio Grande.