He was ordered held in the Linn County Jail without bond.
Helder was flown to Cedar Rapids from Reno, Nev., where he'd been held since his capture Tuesday. He is accused of putting 18 pipe bombs and anti-government letters in mailboxes in Iowa, Illinois, Nebraska, Colorado and Texas.
Six of the bombs exploded last Friday, injuring four letter carriers and two residents.
Helder was charged in Iowa and Illinois with using a pipe bomb in a crime of violence and destroying property used in interstate commerce. He was charged in Nebraska with interstate transportation of explosives and he faces a firearms charge in Nevada.
His parents, Cameron and Pamela Helder of Pine Island, Minn., left Reno on Thursday after a jailhouse visit with their son.
"It's already been very hard on us," said Cameron Helder, who'd tipped the FBI that his son may have been setting the pipe bombs after receiving a letter from Luke. "Our heart goes out to the families of the victims and the victims."
Cameron Helder said he wanted to thank the FBI and the sheriff's department for making the visit possible "so we have a better understanding of what is going through his mind and what is happening."
He declined to take questions and urged the media to leave his family alone.
"We do need our privacy. And the media has really been hounding us. It's tough," he said.
Washoe County Sheriff Dennis Balaam said Helder did not seem upset that his father turned him in.
"I think he understands. I don't think there are any ill feelings there at all," the sheriff said. "It was an emotional goodbye. It's a difficult time for all.
"I think as each moment goes by the consequences are starting to set in with him."
Balaam also said Helder was headed for California when he was arrested, but he did not know why.
Helder told authorities Tuesday that he wanted to create a "smiley face" pattern on the map, a sheriff said.
Authorities say the first 16 bombs were arranged in two circles, one in Illinois and Iowa and the other in Nebraska. On a map, the circles could resemble the eyes of the popular 1970s happiness symbol. The final two bombs, found in Colorado and Texas, form an arc that could be the beginning of a smile.
"There was a comment made to one of my officers about his hope to make a smiley face when he was all finished," Pershing County Sheriff Ron Skinner said.
Skinner said Luke Helder made the comments to an undercover county officer shortly after his arrest outside Reno on Tuesday.
"His demeanor was very jovial. He didn't seem to be taking anything seriously at the time," the sheriff said.
An FBI official would not comment on the sheriff's report.
Authorities said Helder has confessed to making 24 pipe bombs out of smokeless gunpowder, BBs or nails, paper clips and Christmas tree bulbs. The final 10 bombs found in mailboxes and the six found in his car were not rigged to explode, authorities said.
Using a map, Helder had pointed to towns where he placed eight bombs in Illinois and Iowa on Friday, FBI agent Mark Heavrin said in an affidavit.
Helder also described placing other bombs in Nebraska, Colorado and Texas during the weekend and admitted he made 16 more bombs in a room at a Nebraska motel near Omaha, Heavrin said.
Six people — four letter carriers and two residents — were injured by bombs left in mailboxes in Illinois and Iowa.
"On the Iowa charges alone, he faces a mandatory minimum of seven years and a maximum of 40 years on one count and on count two, he faces 30 years to life," Assistant U.S. Attorney Craig Denney said.
Helder was a junior majoring in art and industrial design at the University of Wisconsin-Stout in Menomonie, Wis. Former classmates said Helder loved the grunge band Nirvana and was preoccupied with Kurt Cobain, its lead singer, who committed suicide