I think a lot of people are reluctant to search courthouse records as they have had a bad experience at the courthouse, I know I did, the first time on jury duty was a real bad experience, but that was a long time ago and I will tell about it later.
The county clerk has the records of the courts. Washington has District Courts and Superior Courts in each county, District Courts are mainly for misdemeanors and they only keep records for a few years so probably not much help to genealogists. Superior Courts are the court of record for Washington. Seems like I have heard that phrase before, oh right in naturalization's, before 1906 people filed their naturalization's at any court of record. So what records does the clerk have? Criminal and civil court cases, criminal is self explanatory and if you find your ancestor here you usually have hit the jackpot, they keep a lot of records for criminal cases. Civil cases are all the non criminal cases, divorces, law suits, adoptions, guardianship's, and probates. Adoptions in Washington are sealed forever, takes a court order to open them, and genealogical research will not be enough to convince a judge to open them. Adoptions cause a problem for Spokane County and I suspect all the other counties in Washington also. Spokane county filmed all the civil cases together early on, later they did separate out adoptions and film them separately, so each early roll of microfilm can contain an adoption record. All the other types of civil records on the microfilm are open to the public, so they guard the film pretty well to make sure you do not wander into a protected section of the microfilm. Most people don't think there were a lot of divorces early on, but they would be surprised when they check the films and see how may there are on microfilm. Tip for Spokane county, a lot of people went to Lincoln county for divorces, so if you do not find the divorce in the county they lived in check for a "divorce county nearby". Also a lot of divorced ladies would list themselves as a widow not a divorcee. I have only looked up one guardianship, but it had a bunch of information on the children. Both parents had died, and while they were not wealthy they owned quite a bit of land, the court sold the land and put the money in trust for the children, and every year till the children were 18 the guardian reported how much money had been spent on their care, and when they reached 18 the rest of the money was given to the children. Probates are always interesting and you should always try to find your ancestors probate package. The conventional wisdom is to have a copy made of all the pages in the probate package, but I have a small problem with that sometimes. Each day when the court started they put a page with the date and the name of the judge and the case number, so if they were in court a week you get five of those pages with nothing of genealogical value. When I first started doing courthouse look ups they charged $2 for the first page and then a dollar a page after that. I once looked up a probate that was 365 pages long, so even 5 pages that are unnecessary saves a little. Today they charge 50 cents a page for copies, but that can still add up quickly. You can look at the pages for free. Spokane county has the court records back to 1880, but my experience with the earlier records is the microfilm is very poor, so hard to get a copy. Also the indexes are on microfilm and the early years are very hard to read. Today all the records are being kept on computer and some of them are even showing up online.