The Missouri Valley Bridge & Iron Company built the Oregon Trunk Railroad bridge by cantilevering it out from rock walls on both sides of the canyon.

Near the town of Terrebonne, north of Redmond in Central Oregon's high desert



Construction consisted of lowering all steel needed for the bridge by derrick to the bottom of the canyon and then having men go down rope ladders to attach the steel beams to cables in ordered to hoist them back up again as they were needed!

The first train crossed the bridge only four months after construction began

 Half the rivets holding the bridge together were installed after trains started using the bridge. The bridge was built quickly to facilitate laying the last 25 miles of track to Bend where Jim Hill himself drove the "golden" spike on October 5.

https://mailtribune.com/lifestyle/bridges-over-troubled-waters-amp-8212-spanning-the-crooked-river-canyon
https://trainfanatics.com/oregons-crooked-river-bridge/