Night arrived, and there I stood on the St. Croix River, senses fully alive.

It was mid-February. The temperature hovered in the high teens, and the wind was cold but light.

At the bottom of an embankment for the Stillwater Lift Bridge, Wisconsin side, four friends and I braced ourselves for a run north. Thirty or more runners were preparing for a similar jaunt, only they would head south, launching into the gauzy darkness and their own personal adventures.

The 2014 Full Moon Frozen River Run was underway.

Moving now, our group of five pulled apart — first a few feet, then yards — as we stomped in snowshoes beneath the bridge and out into the wide open of the St. Croix River. Small plumes of snow flew up in rhythmic succession.

Every sort of track — snowmobile, human, animal — marked the way upriver, revealed by the bright white of our headlamps. Snowmobiles had left the biggest impressions, and we gravitated to those. The rough, ribbed tracks were compact in some spots, uneven in others.

Early on, our running was a series of stops and starts as we got our bearings. Sometimes we lined up like GIs at boot camp. Sometimes we spread out wide, seeking a just-perfect footing that didn't exist.

No matter. Running was the perfect vehicle for exploring this wintry night.

The dark gave up its ghosts to our delight. Hulking in silhouette, limestone outcroppings came to life and grew before our eyes as we approached to investigate. Seepage that fed the St. Croix collected at their bases like giant snow cones.

In bursts, we continued to put distance between ourselves and the glow of downtown Stillwater. The darkness deepened and drew us in, the full moon remaining hidden behind a curtain of clouds.

As we neared the St. Croix Boom Site about 3 miles north of downtown, the islands looked majestic in their frozen stillness, the bluffs like sentries, watching us. We passed a few homes that looked warm and inviting atop those bluffs. And yet here we were on the outside, warmed by the fire of adventure — and one heck of a workout.

"Why again did Joel do this?" asked my friend Dan Winga, with a hint of jest as he continued propelling his body forward. "For fun," came the reply. We had a good laugh at that one.

A runner's guiding light

"Joel" is Joel Button of Stillwater, organizer of the Full Moon Frozen River Run.

An ultramarathoner, Button traced the run's history to an itch he felt several years ago to try something "unusual." Listening to that inner voice, he found himself stepping onto the icy river. Sometimes he ran to fish houses in Bayport before turning back.

"All these things sort of came together," he said. "Night running, moony night. I remember running a couple times on the river with the moon out, by myself. I was amazed being able to run completely well."

Then, Button thought, why not invite others?

Button intentionally has kept the river outing informal — it's still little more than a group run, even though the event's safety demands are considerable. The first frozen river run was in 2010, and 11 runners showed up.

Of course, the whole event hinges on the weather. Consistent cold snaps lay a safe foundation for running. Conversely, there have been thaws that have canceled the fun; 2012 didn't happen. "Usually I can't get on the river until January. This year, it was cold sooner," Button said. Runners had at least 3 feet of hard water atop the St. Croix as they traveled this year's routes.

Earlier in the evening, about 8:30, runners had gathered shoulder to shoulder in Button's law office near the Dock Cafe. Shoes were adjusted. Hydration packs positioned just so. Headlamps double-checked for life.

Soft-spoken and friendly, Button also was firm about where to run and where to avoid. River ice can be uneven because of springs and currents. Normally, the run is point to point, from Marine on St. Croix to Stillwater. But the conditions upriver are iffy this year, so Button designated out-and-back routes from Stillwater.

He handed out maps. Runners' names were taken, too, with a strict order to check in with volunteers when we returned.

More than an hour later, we were 4 miles upriver when we decided to turn back. We were tired but still energized by the outing. Feeling more like inhabitants of the river's wondrous night life than mere visitors, we pushed for home.

Bob Timmons • 612-673-7899