What's missing from this picture?

Obviously, snow.

But that doesn't stop Catherine Benson, and it won't stop hundreds of participants -- on skateboards, scooters, sulkies, bicycles, wheelchairs, carts, rollerblades and wheel-equipped "sleds" -- from logging thousands of dog-powered miles this weekend.

Benson, who operates Maryland Dog Sled Adventures, will be among those taking part in "Dogs Across America," a nationwide event that started three years ago and one that demonstrates just how much pull dogs have in this country.

This year, organizers are hoping to hit the 3,000-mile mark.

Dog scooterers, mushers, and other participants in dog-powered sports organized the relay-type event to demonstrate the pulling and traveling ability of dogs.

In each participating state, teams of dogs and humans will run one or more trails in the state, with the miles each human covers going toward that state's tally.

The event is held over three weekends -- Oct. 20-21 in Canada and Alaska, Nov. 10-11 in northern states (including Maryland), and Dec. 15-16 in southern States.

In Maryland, some participants will follow the Northern Central Rail Trail in northern Baltimore County, from Freeland to the Pennsylvania state line and back (starting at 10 a.m.) -- with dogs pulling them on bikes, carts and, as is the case with Benson, in a sled equipped to run on dry land.

The number of dogs per device is unlimited. Should there be snow, skis and sleds will travel the trails. Otherwise, any wheeled device may be used. Dogs can pull scooters, bicycles, sulkies, dryland mushing rigs, wagons, carts, roller blades, roller skis, skateboards, wheelchairs or even just a human walking behind them on a leash.

Dogs Across America describes itself as "a loose group of dog lovers," many of whom connected through the Yahoo Group "DogsLoveToRun."

Having a dog tug you across terrain seems to be an up and coming sport -- one whose level of human exertion, at first glance, appeals to me

We'll take a closer look at dog-powered sports in the days ahead -- or at least the next two.

Thursday we'll cover some dog scootering basics

Friday we'll look at the new company, Maryland Sled Dog Adventures

As for Saturday, there's still room to mush (dry style) if you want to get in on the action.