Wallula Gap is near the TriCities and is named for a spot where the Columbia River passes through a relatively narrow spot. It's essentially another shorter Columbia River Gorge.
There are basically two main attractions. First is to drive the south and east side of the Columbia on US730. This passes a small recreation area called Sand Station Recreation Aea. It has campsites, picnic spots, and view.
The Columbia turns north in this area and is no longer the state border. US 730 follows the east side but there is no road on the west side. A couple of miles before the junction with US 12, there is a small pullout for the very short hike on the prominent Twin Sisters. The trail is not much more than a quarter mile, but has great views. The trail leads up to the shelf at the mid-level and you can get into the saddle between them, which on this day was quite the wind-tunnel.
But the main appeal is the hike to the bluff of the Wallula Gap gorge on the west side. I used the book Washington's Channeled Scablands Guide to find the trailhead, which has no signage. From Twin Sisters, you have to drive north to Pasco, cross over to Kennewick and drive south 15 miles (to the town of Finaley an then on roads Piert, Meals and Avery to it's end), the last two miles on a well-graded gravel road. Access to the hike was blocked by barbed wire, but no signs regarding tresspassing, so I found my way over it.
The hike itself was about 7 miles RT and there are many intersecting trails up there again with no signage, so you have to make some guesses. But with the river usually in view, it's not as hard as it sounds. The hike mixes dirt roads with single track trails. Like Catherine Creek or the Labyrinth, it is open grasslands up there and plenty of exploring is possible.
It's about 3 miles and 800 foot gain to a radio tower that gets the first view from the bluff. There are many more promontories farther on, some of which require inland detours around deep canyons.
On the way, I had a good view back to Twin Sisters.
The generally open terrain up there
One of the views. I did continue out to the point you see here. It was more south facing, and the more south-facing on that day, the worse the winds.
I saw a herd of deer, maybe 20 of them, in the distance. This is the only picture that came out well. At first, I thought they were pronghorn, but hooking more closely, it appears they were deer.
As you could see, 100% sun, temps in the lower 50s, and breezy. Didn't see a single person up there and my car was the only one at the trailhead.