In his sixth - or perhaps seventh - pair of running shoes this year, David Wilcox, 15, ran from the Liberty Bell in Philadelphia to downtown Collingswood. His father, Brett, his aunt, Julie Stuehser, and the family dog, Jenna, ran along with him.

Since January, David and Brett Wilcox have been running across the country, 20 miles a day, to promote awareness of genetically modified organisms and mandatory GMO labeling on products.

The journey started in a Los Angeles suburb; the goal is to reach Ocean City, N.J., which could be accomplished in days. As they jog through neighborhoods and encounter passersby, the father-and-son team hands out seeds and hopes the message will germinate.

"I've been phrasing him as the modern-day Johnny Appleseed," said Karen Stark, cofounder of the group GMO Free Pennsylvania.

Coming off the Ben Franklin Bridge, David and Brett ran through the streets of Camden. They talked with people out on their porches Thursday afternoon, inquiring about their food choices and what they knew about GMOs.

Waiting in downtown Collingswood with a dozen supporters of GMO labeling was Kris Wilcox, David's mother. She prepared a camera and microphone setup to record the small ceremony that would take place once the runners arrived.

Kris and Olivia, David's little sister, have been making the trip as well, tasked with finding the next spot to park their trailer - pulled by a 1998 Ford F50 they bought for $4,900 with 109,000 miles on the odometer. They've added about 3,000 more as they've made their way to Ocean City.

"I think they've stopped to talk to a few people," she said, peering down Haddon Avenue, wondering where they were. As a runner approached, the cheers increased, but it was a false alarm - just another jogger.

Along the way, Kris has been faced head on with the message they're trying to address. When looking for food, it's hard to find what they want to keep their family healthy - GMOs are ubiquitous. Passing through northern Arizona and New Mexico, they simply stopped buying corn tortillas. Their time going through the Navajo Nation was their one reprieve; they took a chance on Navajo cornmeal.

Brett Wilcox is a mental-health therapist who quit his job for the cross-country run. To fund the effort, they've rented their house in Sitka, Alaska, and started an Indiegogo campaign. Brett also wrote a book, We're Monsanto: Feeding the World, Lie After Lie. They accept donations at

GMOs have been scrutinized recently as more consumers raise concerns that the foods are harmful to people. GMO Free Pennsylvania and GMO Free New Jersey are two groups working to influence state legislators to require GMO labeling on food packaging. They also hold rallies to raise awareness.

One modification often cited by GMO opponents makes plants resistant to herbicides, allowing farmers to spray the herbicide liberally to kill weeds. The action breeds "super weeds," which require even more treatment of the crops.

Monsanto, the world's leading producer of genetically modified seeds and herbicides, says on its website that genetically altered foods are necessary to meet increasing food demand globally. The website adds that engineered scientific advances have been at the front of historic human advancement.

In New Jersey, efforts to pass legislation that would require GMO foods to be labeled as such are "stalled in committee," according to Barbara Thomas, cofounder of GMO Free New Jersey. The legislation has popular support, she said, but has been met with difficulties from individual lawmakers.

Back in Collingswood on Thursday, the father and son came into sight. They are almost at the end of their journey - one partially inspired by David's desire to one-up a 17-year-old girl who had run across the country.

The Wilcox family brought a father's passion for GMO advocacy together with a son's passion for competition and long-distance running.

"We ran 3,000 miles for this!" Brett Wilcox said, thrusting his arms into the air victoriously as they reached the crowd. "Yes! Somebody cares!"