Tigard

"We flew in low over what remains of Tigard. It was raining dark mud like rain and lightning filled the clouds but never really formed any streaks or strikes. Fires still littered the ground, breaking through from under the surface to flare up.  I thought it would be quiet but it wasn’t.  It was as if a thousand windows were being broken, the wind formed shrill almost animal like sounds, and the rolling thunder shook me.  No one down there could have survived.  There was no safe LZ in Tigard so only visual passes like this one have been made."

- Paul, a UNSC civilian reporter attached to Spirit of Fire.

Tigard was a town on Harvest, in the northern regions of the planet, near a Forerunner Relic. During the glassing of the planet by the Covenant it became an inhospitable wasteland. A UNSC base was established in 2526, Alpha Base, which managed to capture and observe a Forerunner relic in 2531 for a short amount of time before the Covenant retook it, leading the Spirit of Fire to Arcadia.

Given that the majority of Harvest's population were originally from the American mid-west, Tigard may have been named after the town of the same name.