Plants won't keep the dogs out. You'll need some kind of physical barrier they can't push through. Maybe the wire fence will do it. However, beware of wire fencing over lawn as the grass will grow up through the wire and be impossible to cut, unless you leave a gap underneath.

If you live in a maritime area (Vancouver, Seattle, Portland...) Pacific wax myrtle (Myrica californica) shoots up pretty quickly when happy and can be bought in one gallon pot sizes. Being native many retail outlets stock it as native plants are in fashion - and growers apparently don't find it hard to produce.

Most living in the maritime northwest are in USDA 8.

Here is a link that might be useful: Raintree Nursery, USDA hardiness map, climate zones, growing zones

A lot 100' along each side will likely have a number of planting conditions varying from full sun to various degrees of shade, as well as a range of soil conditions to consider, so a single plant choice may not be ideal. And depending on how it was handled, a single choice could also be consumately boring :-))

You might want to do some research on tapestry hedges or hedgerows. These typically include a mixture of shrubs and sometimes small trees, both evergreen and deciduous, so offer a much greater aesthetic appeal as well attracting birds and other wildlife. These can be sheared into a more formal, hedged shape or, if space allows, left to grow naturally (my preference). Since we are not in the slightest bit limited in our climate by the variety of shrubs we are able to grow, you are ony limited in your choices by the conditions and your own creativity. Most better local nurseries and garden centers will soon be offering a full compliment of stock from which to choose.

Rather than chicken wire, which tends to be rather flimsy, I'd look into steel mesh. More expensive but also far more durable and a bit more of a refined look if well constructed. You can get the mesh in various sizes - the larger the squares, the lower the price and even larger squares (2-3") will have the same barrier effect. The problems with grasses or weeds that bboy mentions will still exist so best to keep the area cleared or use larger plants and mulch.

I found that the only way to keep my own dog IN with a wire fence is to allow the plants to grow up the wire material, to anchor it to the ground. Anything will do - even bentgrass. Blackberry is best anchor plant though. My 60lb boxer mix can squeeze under pretty much any wire fence that is not anchored with bentgrass or blackberry. Mahonia and salal don't quite cut it, she's gotten out through a tunnel pushed through the salal.

On the other hand, friends with a similarly sized dog had no fence at all, just a holly and cotoneaster hedge, and he never got out through holes large enough for me to crawl through - he didn't want to go anywhere.

All will depend on how badly the neighborhood dogs want to get in. Mine pushed her way through barbed wire.

Chicken wire will not keep any but the wimpiest dogs out. Cheap wire mesh fencing sold at big box stores will not either, I have a couple of neighbors with that kind of fence and their dogs are constantly getting out and wandering off.

100ft square is not at all a lot of fence. I had to fence in 5 acres once, that is a lot of fence. Farm fencing comes in 100 ft rolls. I use the horse fencing, it's the sturdiest, also heavy and about $125 for 100ft, but either you're serious about a fence or you're not. The mesh is 2" by 3" I think, and heavy gauge wire. Hog fence might work if your neighborhood dogs are wimpy, it's much lighter and less expensive than horse fence. It has smaller holes at the bottom and larger at the top where the animals are less likely to go through them, although my dogs would push their heads through the hog fence and then get their collars stuck.

If you just want something to discourage dogs that are not determined to get in anyway, like they aren't being attracted by your other animals or kids, then you just want something low and bushy and thorny. A tall hedge won't do it, they're too woody and bare at the base, like my friend's holly hedge. Blackberries work best. Or low moundy roses with lots of thorns.

One compromise is one kind of hedge on each side. A rectangular lot would then have four kinds of hedges. It depends on what you are going to do in front of the hedge. If the hedge is to become a backdrop for other plantings or other things (play equipment, gazebo, table and chairs) that are to be the focus of attention then it may actually be preferable for the hedge to be comparatively inconspicuous or uninteresting. Something as complex a feature as a mixed border may have a sheared hedge made up of some small-leaved, fine-textured selection like yew or box to form a fence-like contrasting backdrop to the blowsiness and business of the mixed border occupants in front of it.

Thanks to you all for your time and ideas! You have some great suggestions. I think we might just do one side at a time and see how it goes. maybe we'll mix it up a bit.

I like the idea of the blackberry bushes just because they are impenetrable once they take hold. OTOH, I'm not sure if we could contain them.

And it's also good to consider the heavier weighted wire. We are planning on staking the bottom of the wire in the ground and then burying it.

Thank you all again!
Lanni