They built one pipeline through South Dakota, but President Barack Obama doesn't want TransCanada to build a second oil pipeline through the state.
The president has denied the permit TransCanada needs to build a 1,700 mile pipeline from Alberta to Texas.
The pipeline would have cut through Western South Dakota.
The president was supposed to make a decision on Keystone XL before the end of 2011, but he decided to delay approval of the permit until early 2013 because he said officials needed more time to study the project and re-route the pipeline around the Nebraska Sandhills.
Republicans pushed for legislation that would force a decision in 60 days. The legislation passed, requiring the president to make up his mind by the end of February.
Now, the president has denied the permit saying 60 days isn't enough time to study all the impacts. If TransCanada wants to build the Keystone XL pipeline, the company will have to start the entire Presidential Permitting process over.
"I think it's really good news for South Dakota. The president looked at it and decided to stand with South Dakota landowners who have been opposed to this project, and believed it was a threat to our health and safety, and believed that it just wasn't in our national interest," Matt McGovern with the National Wildlife Federation said.
McGovern is opposed to the Keystone XL project. He says landowners who would have had the pipeline built on their property are pleased with the president's decision.
"I'm just grateful that the president stood with the landowners in South Dakota and other people that had expressed their concerns in wanting to protect our land and water from this project," McGovern said.
But South Dakota Senator John Thune says the president's decision wasn't about the pipeline, but about scoring valuable political points with environmentalists.
"I think he made a very political decision. He's going to run for re-election this year. He didn't want to antagonize certain parts of his political base, so he decided to turn it down," Thune said.
While Thune realizes there was opposition to this project in the state, he says the pipeline could have brought jobs and added tax revenues to small struggling counties in western South Dakota.
"There are some landowners and some environmental groups who don't want to see the project proceed, but if you look at the vast majority of South Dakotans, they recognize not only the economic value and the jobs it would create but they also recognize it would generate a lot of tax revenue for state and local governments," Thune said.
The only way the project can happen now is if TransCanada starts the permitting process over, and the Canadian company says in a news release that's what it intends to do.
The President and CEO of TransCanada says they will re-apply for the Presidential Permit and still hope to have the pipeline up and running by 2014.