After a little prodding from Lost Rail's good friend, Oil-Electric, I've put together a link to the bridge abutment's location on the western edge of Spokane:
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The abutment stands, more or less, at the point where W. Ohio Ave and N. Summit meet and points south-east in the above photo. From here, the old trestle in question would have crossed the Spokane River and Hangman creek on its way across the valley. A walking bridge now spans the River in the approximate location of the old trestle piers. When the water level is lower, these are still visible just east of the walking bridge, however, seem covered in the image above.
Also of interest, to the north and east of the abutment are the remains of the old UP round house, still visible from above. Spokane was quite the railroad town...