Simple question. Oh if you post, make sure you note your location.
There’s a Portland, Maine?
Yup. Two men founded Portland, OR. One was from Boston, the other was from Portland, ME. Each wanted to name the city after is own home city, so they decided the issue by flipping a coin. Portland won:
[QUOTE=Wikipedia]
In 1843, William Overton saw great commercial potential for this land but lacked the funds required to file a land claim. He struck a bargain with his partner, Asa Lovejoy of Boston, Massachusetts: for 25¢, Overton would share his claim to the 640-acre (2.6 km2) site. Overton later sold his half of the claim to Francis W. Pettygrove of Portland, Maine. Pettygrove and Lovejoy each wished to name the new city after his respective home town. In 1845, this controversy was settled with a coin toss, which Pettygrove won in a series of two out of three tosses.[1] The coin used for this decision, now known as the Portland Penny, is on display in the headquarters of the Oregon Historical Society.
[/QUOTE]
I think of Portland, Oregon, because I grew up in Vancouver, Washington, directly across the Columbia River from Portland.
Generally I’d think Oregon as that is the big Portland, but I live in CT so in the right context like “I’m going to drive to Portland for the weekend” or if I knew the person spent time in Maine, I’d know it was Portland, Maine.
Having been to both - I go with Oregon.
Portland Maine has all of the Maine-ness, and it is indeed an ocean port, while Portland Oregon is only a river port. But port-ness aside, there is no comparison.
Portland Oregon is it’s own place, with it’s own vibe, weirdness and hipsters and west coast outdoorsy capital “L” liberalism, and it’s own gently mocking TV show. Portland Maine - not so much.
I voted for Maine because I live in New England.
Portland Maine is the default here because it is relatively close. But we usually don’t have to specify even when referring to the Oregon one. My husband has business travel to Portland Oregon, and when he does he just says Portland. Since we know work stuff is in Oregon, further clarification isn’t necessary.
Maine. I’m a New Englander 
Portland, OR. I live in OR. No one out here means Portland, ME, unless they specify ME.
Oregon.
I’m on the west coast.
Portland, Oregon-Beervania!
Portland, Oregon, where twenty-somethings go to retire. Portland, Oregon, where the street names are eerily reminiscent of Simpsons characters. Portland, Oregon, where the beer is plentiful, and the sun shines … well, once in awhile.
All I know about Portland, Maine is that it exists, and is probably in Maine.
Portland, Oregon.
I’ve been to both cities, but had a lot more fun in the western Portland.
Portland, ME. I live north of Augusta, Maine.
I think of the Oregon version and have my whole life. Born in CA, living in WA now.
Oregon.
I’ve lived my entire life in California.
Since I live in the Willamette Valley, any mention of Portland around here is refering to Hipsterville.
Maine, but only because I’m a lot closer to it than to Oregon.
Spent a fair amount of time in both places, and they’re both great.
When I was growing up in NY state, Portland always meant Maine. When I lived in the midwest, it still meant Maine. When I moved to the west coast, it always meant Oregon. Then the place became a Hipster Heaven, so it became more culturally prominant. I’m back on the east coast again, and no longer have a default setting. Thus, whether I think OR or ME depends on context and who is speaking…which city is meant runs 50-50.
I have enjoyed time in both cities, but would rather live in the Maine version, if I had to choose. Something seems a bit too precious and not quite real about the Oregon version.
OR, even though I have lived most of my life on the east coast. I can’t recall ever having been in Portland, ME and I am sure I have never been in Portland, OR.
The pole said “if you hear” so I’d say Portland, ME because I’m in Portland, ME. If I see it on the web, I think of Portland, Oregon because it usually is.