This ain’t no stroll in the canyon.

This is the Western States Endurance Run, the mother of all ultra-running events — and it’s happening right in your backyard.

Here’s everything you need to know about this year’s run:

The return

For the first time in history, the 2008 Western States Endurance Run was cancelled due to wildfires and ensuing smoke that would have made the 100-mile trek even more treacherous for runners.

“It was a tough-but-necessary decision I think,” said race spokesman John Trent. “It was a real downer last year, but the enthusiasm and love everyone has been showing the race this year has been remarkable. You take a race like Western States for granted until you don’t have it.”

Runners who were signed up for last year’s run got first dibs on entering this year, he said.

The history

The Western States is the oldest ultra marathon in the West. It was first run in 1974 by Meadow Vista's Gordy Ainsleigh, who tagged along with the horses covering the trail during that year’s Tevis Cup ride, proving the feat could be accomplished on two legs. The first official run was held in 1977.

“It is the grandfather of the ultra-running events,” said Cynci Calvin, Auburn Endurance Capital Committee member. “This one is the one that launched the world of ultra running. We can take a lot of credit that this all started right here and had a ripple effect around the world.”

The trail

The Western States Trail runs from Squaw Valley to Auburn. During the 100-mile stretch, runners climb more than 17,000 feet and descend more than 22,000 feet. The trail also includes a fording of the American River at Ruck-A-Chucky (aka a cooling soak for overheated runners).

The timing

Runners start at 5 a.m. Saturday and run overnight (yes, in the dark with flashlights) to reach the finish. Runners must complete the course within 24 hours for a silver Western States Buckle, and under 30 for a bronze one.

The aid

Runners encounter 25 checkpoints, 10 of which have medical aid stations where they are monitored for dehydration and exhaustion. The athletes also stock up on carbs and salty foods at aid stations, shoving bananas, potatoes, pretzels and energy-packed goo into their mouths before hitting the trail again.

The runners

There are 445 participants this year from as far away as Italy, Japan, New Zealand and Tanzania who have been training for six months or more.

Some are mega athletes, others are mortgage brokers, software engineers, nurses and retirees.

“There’s a wide range of people, those with incredible talents and physical attributes right down to the average Joe,” Calvin said.

The ones to watch

Spectators are in for an exciting run this year.

“The level of competitiveness at the front of pack is unprecedented,” Trent said.

Seven-time first-place finisher Scott Jurek (bib No. 11) returns this year. Jurek holds the record for fastest time, breezing through the grueling course in a measly 15 hours, 36 minutes and 27 seconds in 2004. Also competing is Brian Morrison (bib No. 30), who was disqualified from winning in 2006 after a dramatic finish in which he was assisted around the Placer High School track by his pacer — Jurek.

Four-time finisher Nikki Kimball (bib No. F1) of Bozeman, Mont., will try to improve on her personal best finish time of 18:12:37 in 2007. Second-place women’s finisher three years running, Beverley Anderson-Abbs (bib No. F2), will also try to capture a women’s win.

The volunteers

Between medical personnel, river-crossing aides, trail sweepers and communications personnel, more than 1,000 volunteers help pull off this event.

The crew

Runners are assisted by crews that are allowed to supply food, shoes, sunblock and other materials — not to mention a dose of encouragement — at certain checkpoints. Runners are also allowed a pacer to accompany them starting at the Foresthill aid station.