In order to have a decent fair, you must have something new and exciting to offer the public each year, along with popular actives that people come back for year after year.
You must advertise several months ahead of time, every week, newspaper ads, and local radio ads, St. Helens, Scappoose, Vernonia, Rainier (Longview daily news) Clatskanie along with Hillsboro and Portland ads. In these ads you need to advertise the events too.
Get all local industry to have displays explaining their manufacturing processes, that would be Boise, Costal Chemical, Armstrong, Cat litter place (Columbia City) Scappoose airport business, Simpson lumber, Pacific Stainless etc…
US Gypsum, Ethanol plant, PUD, PGE,
Use out of town business also, such as Tillamook Cheese and whatever new and exciting business would want to come, reach out and contact what you might find interesting. Do not charge for them to set up, only take a small percentage of their profits, if they sell items, idea is not to charge so much that they would not come.
Contact radio stations in Portland or Longview and see if they would donate money to sponsor the fair or big attractions, like a blues band, or Sweet Baby James. Call on KOHI to do something too.
again draw people in on nights other than rodeo nights, you may get people to come more than once
Use the local Historical Society, and also the state historical society, have them a nice place to offer historic information about the early days of the county, with some displays, and printed information, let them sell handbooks if they want and let them keep the money, again they would bring in more people, you would make up the money through attendance.
Have the Port of St. Helens do a display of their big job at Port Westward, with aerial photos, and inside photo's of the ethanol plant being constructed, people would find this interesting, many people do not realize what it looks like building something of this nature.
Contact local unions and see if they would be interested in setting up displays explaining their work (these would be a free admittance to the display folks (all this would bring people in and give people something to look at, making them spend more time at the fair which in turn would have them spend more money for food/ goodies.. Also they would come with friend's especially older folks if there were more exhibits.
Call the OWDF or Oregon Fish and Game and have them bring in their education exhibit
Have the corporations sponsor (each) some event for the fair, such as a clown for kids day and all day sat, or the worlds biggest pig, or steer anything, or band together and sponsor a big event on Thursday night After all the corporations are receiving A FREE OR REDUCED TAX RATE an this would show community support a gesture of good will you might say.
Contact the Sr. high and see if the shop teacher would set up an area for shop projects display, contact the school and see if they would have time to let the kids do projects so they could submit them for display and judge them, show the public their welding skills, or wood working skills, with samples of their skills and judge them for a prize, offer a contest between all the shop classes from all the schools in the county and judge them for a ribbon and cash prize. More participation!!
Advertise THE Local Food bank, that if you bring along a can of food you get into the fair $1.00 cheaper if not charge THE $1.00 AND DONATE IT TO THE FOOD BANK.

Have a little kid farm scramble with the kids chasing chickens in the rodeo arena, especially on Saturday this would bring in the whole family
High school jazz band perform, people would come to listen to their kids, grandma and grandpa, aunts, uncles, and they would bring their family again these people would spend money.
Have a clown walk around making animal's out of balloons, giving them to the kids,
My favorite Organ grinder and monkey
Guy on Stilts
A singing rover
These are just some creative idea's to get you thinking!
See if the car clubs would show their cars
BBQ Cook Off
Hot Dog eating Contest
Pie eating Contest
Chili Cook Off
Charge a reasonable entry fee, to pay for the winner's prize.

Have a tractor pull, or something for young people ( a band)
Finance things like Brads World of reptiles,
Have OMSI come in
Have the zoo bring in their educational unit.
Petting zoo
Face Painting
Contact the fiddlers association and see if they would come in,

Have a Jr. Rodeo, with prizes.
Have a Pee Wee rodeo with the small kids riding sheep and award prizes.
Have chariot races with Shetland horses or chuck wagon races around the rodeo arena
Have lawn mower races on Saturday afternoon, with the final race off before the rodeo Saturday night with a silly trophy ages 16 and older
Have a greased pig race
Wild cow milking contest

Have local ladies judge the quilts and crafts, cakes etc. We have professional cake decorators that can judge cakes and cookies etc. ladies that have led girl scouts, 4 H, Sr. ladies come and judge the sewing, crocheting, foods, I believe that they have done hundreds of projects and they could do just fine. Or have both, they could do those jobs very easy and that would cut costs.
Contact the Sr. high and see if the shop teacher would set up an area for shop projects display, contact the school and see if they would have time to let the kids do projects so they could submit them for display and judge them, show the public their welding skills, or woodworking skills with small samples of their work and judge them for a prize, offer a contest between all the shop classes from all the schools in the county and judge them for a ribbon and cash prize.