There is no obvious reason that California condors could not be reestablished in the Pacific Northwest. Although we don't know the exact causes of their disappearance, all available evidence points to direct human-caused mortality as the key agent. There is no evidence that the natural environment is any less favorable for condors now than it ever was.
From a purely technical standpoint, there are few places in northern California, Oregon, and perhaps Washington that could not be selected for condor releases. The releases in northern Arizona (not condor habitat since the end of the Pleistocene) and Baja California (poor condor habitat since the 1930s) show that - with a commitment to long-term intensive management and manipulation - a condor population might be maintained almost anywhere.
Having opened the introduction door wide, I suggest there are good historical, biological, socio-political, and esthetic reasons to close it halfway, to consider only those areas in Oregon west from the west slope of the Cascades, and in California west from the Sierra Nevada foothills to the Pacific Ocean.
1. Historical - There is no evidence that condors were ever resident east of the Cascades or east of the Sierra Nevada. If there were resident condors in Washington north from the Columbia River, they were found west of the Cascades. In general, introducing condors where the species once occurred seems more logical than putting them where they didn't exist.
2. Biological - The lack of resident condors east of the mountains was probably food related and climate related. The intermountain West did not support dense or widespread populations of large mammals. In the west, there were more species in larger numbers than in the east, and the western area also provided marine mammals along the Pacific coast. With the introduction of domestic livestock in the mid-1800s, the food supply for condors in the intermountain area improved, but still did not rival the diversity of the west side.
The intermountain area is a region of climatic extremes, with long, clear, warm summers that (given good habitat) should meet condor requirements. However, the winters are long and cold, with considerable snow cover and extensive areas subject to temperature inversions and freezing fogs. The western regions have more local climates and more habitat diversity than the east, which increases the species' options for finding suitable habitat at all times of the year.
3. Socio-political - The intermountain West is historically a region harboring strong anti-government feelings, where a large share of the residents resent and are suspicious of any government action. Programs like endangered species preservation, which raise the specter of government interference and more rules and regulations, are particularly unwelcome. The early days of the Arizona introduction were plagued by incidents involving local members of the "sagebrush rebellion" who resented the attempts to establish a new endangered species on "their" land.
This anti-government sentiment might interfere with establishing a condor reintroduction program in southwest Oregon. However, southwest Oregon has a growing "liberal" population as well as the traditional conservatives, so support would likely be easier to develop that it would be east of the mountains. Elsewhere in the Pacific Northwest, "sagebrush rebellion" resentment and opposition should not be an issue.
4. Esthetics - I admit to being a biological traditionalist, and was opposed to the "biological tinkering" that resulted in Andean condors being released (temporarily) in California condor habitat, and condors being placed in non-condor habitat in Arizona. Releasing condors in, say, eastern Oregon is in my opinion an extension of the game farm mentality that dominated the wildlife management profession for so many decades. Trying to establish new populations of turkey, pheasant, quail, and hundreds of other game birds and mammals so hunters can have more variety to shoot at doesn't seem that different to me than starting extralimital populations of condors "just because we can."
I've suggested a number of general areas that seem to me to have equally good potential for supporting California condor populations. Specific locations within these general regions would have to be determined by field surveys. The only factors that might make one area better to start with than another would be if the level of knowledge of one area far exceeded what is known about the others, and if a particular area already has an active group working toward an introduction. The location that currently separates itself from the others is northern Humboldt County, California, where the Yuroks are already pursuing a condor reintroduction.
Good analyses are available of what condor nest sites in central and southern California in the 1800s and 1900s looked like [e.g., Snyder, Ramey and Sibley, Condor (1986) 88(2):228-241]. Height, aspect, cave depth, prevailing winds, etc., can all be used to select the new release sites. However, it should be remembered that there are few places in the Pacific Northwest that look like the Sespe Condor Sanctuary, so condors nesting there in the past were clearly using what (on the basis of the known nest sites) would be considered atypical. Cathartid vultures generally are very adaptable in their selection of nest sites, using caves, talus piles, bushes, trees, barns, etc. Lacking specific information on where condors nesting in the Northwest, planners should be imaginative. For example, an otherwise good looking area without a good nest cave might be made perfect with a little judicious use of cement or fiberglass.
If release areas are proposed in western areas of Oregon or California, I would expect that most public response would be favorable. The only issue I know of that could side track an otherwise good plan would be the issue of lead poisoning. The targeting of hunters' bullets as the source of lead contamination is, so far, based on faulty science. A scientifically planned study of condor food resources should be done within the current condor range, either to verify the speculation or identify the real source of contamination. Any area proposed for a new introduction should, at minimum, have potential condor food supply and other scavengers tested for lead contamination.