Our climbing team from Oregon will be attempting Rainier's Emmons-Winthrop route in mid-July. We're interested in renting gear like boots and personal locating beacons, avalanche transceivers, etc. on our way to the National Park. Our shortest driving route will take I-5 from the south and turn east before we hit Centralia. Is there a good mountain supply store on our route or would we need to go further north before turning east?

Whitaker Mountaineering in Ashford just outside the southern park entrance would be your best bet. I have had very good experiences dealing with them. I would call them to see if you need to reserve rental items so you don't get to the park and find they have rented the last pair of boots or whatever. Other than that the REI in Tacoma might be your second best bet but would would require driving farther north.