Minority Democrats dragged out debate for nearly nine-and-a-half hours but were powerless to stop the measure. Republicans finally approved it on a 58-39 party-line vote.
The bill already has cleared the Senate. It now heads to Walker, who has touted the proposal as his key job creation plan. He is expected to sign it into law early next week.
"On behalf of the unemployed skilled workers in our state who will benefit from the thousands of mining-related jobs over the next few years, I say thank you," Walker said in a statement.
It's still unclear whether the bill will survive legal scrutiny, though. Conservation groups and the Bad River Band of Lake Superior Chippewa contend the bill eviscerates environmental protections and are considering lawsuits.
Still, the vote was cathartic for Republicans. They've been working for two years to pass a bill to help Gogebic Taconite dig a miles-long open-pit iron mine in the Penokee Hills just south of Lake Superior.
The GOP has played up the mine as a huge economic engine, saying it would create hundreds of jobs for the impoverished region and thousands more across the state's heavy equipment manufacturing sector. But company officials have refused to move forward until lawmakers eased the regulatory path for them.
Republicans introduced a sweeping bill that would have overhauled the state's mining rules in late 2011. Conservationists and Democrats contended the measure relaxed environmental standards and opened the door for pollution that would ruin one of the last pristine areas in the state.
One of the fiercest environmental debates Wisconsin has seen in years ensued. The measure ultimately died in the Senate by one vote after moderate Republican Dale Schultz sided with Democrats against it.
But voters handed Republicans a two-member majority in the Senate in last November's elections, making Schultz's vote irrelevant. The GOP reintroduced the bill this past January, labeling the drive toward passage "Mining for Jobs." The Senate passed it by one vote last week.
The outcome was never in doubt in the Assembly, where Republicans hold a 59-39 majority. Democrats still stalled for hours, ripping the bill as a corporate give-away. They said legal challenges will tie up the project for years and the promised jobs will never materialize.
Republicans accused Democrats of concocting wild worst-case scenarios. They insisted modern mining technology and state and federal oversight will protect the environment and the mine will provide desperately needed jobs.
"Once this bill passes, the state of Wisconsin is not going to get wiped off the face of the earth," said the bill's main sponsor, Rep. Mark Honadel, R-South Milwaukee. "Even though the iron ore may be buried deep in the ground, please don't bury jobs with it."
Under the plan, state environmental officials would have up to 480 days to make a permitting decision. Currently, they face no hard deadline. The public couldn't challenge a permit decision until after it has been made.
The bill also would create a presumption that damage to wetlands is necessary. Applicants would have to submit a plan to compensate for wetlands damage, including a proposal to create up to an acre and a half of new wetlands for every acre impacted, but Democrats argue such mitigation projects rarely work.
A mining company's permit application fees would be capped at $2 million plus DNR wetland mapping expenses. Tax on a company's revenue would be split 60-40 between local governments and the state. Current law imposes no cap on application fees and funnels 100 per cent of revenue taxes to local governments to offset mining impacts.
The bill also exempts mining companies from the state's $7 per ton recycling fee on waste materials, sparing Gogebic Taconite from paying the state an estimated $171 million annually for environmental protection programs.
Gogebic Taconite President Bill Williams didn't immediately return a message Thursday evening.
Assembly Republicans were visibly relieved after the vote, even taking the unusual step of applauding the Legislature's lawyers for crafting and re-crafting the bill.
They walked out of the chamber to find about 20 protesters waiting for them. They hurled insults at the legislators, calling them "fascist pigs" and "traitors." Rep. Brett Hulsey, D-Madison, exchanged a fist bump with one of the protesters and assured them the mine would never happen.
Indeed, the Bad River could prove to be an especially formidable legal foe for Gogebic Taconite. The tribe's reservation lies just downstream from the mine site and members fear run-off from waste rock will pollute their water. As a sovereign nation, the tribe could evoke a host of unique environmental rights in court.
Bad River Chairman Mike Wiggins Jr. promised "active resistance" that could include filing lawsuits to stop the permitting process or occupying the mine site. The Bad River's reservation is sacred and tribal members won't allow it to be polluted, he said.
"We have nowhere to run," Wiggins said.
Associated Press writer Scott Bauer contributed to this report.