From only a "personal opinion" based on some 30 years of genealogy work, you probably won't find the person living in Hillsboro.Even if there WAS a "D. Wright" in the county at that time, it would have to be proven this person painted the picture.
First, take a very close look at the signature.I'm sure you have, but make sure the "D" is not an "S".Look at the back also to see if there is anything written there.Make sure it is an oil and is not a print.You might want to have it examined by a professional.They could tell you if it is an original, a copy, has value, date the oils to verify age, etc.
Look at OLD family indoor photographs, see if you see it hanging on the wall.Since it was dated 1927, chances of seeing or remembering any oil tubes, brushes, palettes, etc. are remote; but try to remember ever seeing that.You indicate you hadn't seen it before, so it might have come to her late in her life.Where was it when you found it?Wrapped up in a closet, storage, or on a wall in the back room or basement?Was it something she may have picked up at a "yard sale" and hadn't really taken care of it; or something that was well wrapped up and protected?
As you indicated all the persons worthy of interviewing have passed.I'd first suspect your grandfather Wright, but if he died in 1923, that probably prevented him from painting it.His and your father's middle name of David, does raise eyebrows.I'd also suspect your father, but if he was born in 1919, then if he did paint it, he missed his calling.
The 1920 Census for Portland
Jay Wright, 33, born in Iowa, to father born Iowa, mother born Utah (? very light copy of census), a police officer.
Clara 36, born in Missouri?
Lucile (as spelled) 4 7/12, born in Utah
Jack, 1 2/12, born in Oregon.
The World War I Draft Card Image database shows Jay David Wright at 761(767? image written over at that point) E 21st Street Portland, OR, born Jan 27, 1886.Employed by the State of Oregon as a State Police(man).Nearest relative Clara Marie Wright.He was tall, medium in build, blue eyes and light brown hair.
The 1910 Census for Ogden, Weber Co, Utah
Nettie? Wright, age 46, widow, born in Utah to both parents born inEngland.She was a Nurse.Mother of 6(probably a 6), 4 living.
James D, son, age 22, born in Iowa, signal man on the railroad.
Margaret, daughter, age 19, born in Colorado.
The 1900 Census for Marriotts, Weber Co, Utah
James A Wright, born April 1857 in Iowa to father born in Kentucky, mother in Indiana, farmer, rents his land.
Nettie A, born Mar 1864 in Utah
Blaud (Bland, as other n's are written as "u") E, daughter, June 1883, born in Utah to father born in Kentucky, mother in Utah
James d, son, born Jan 1888 in Iowa to father born in Kentucky, mother in Utah.
Margarett (as written), born April 1891 in Colorado to father born in Kentucky, mother in Utah.
--All children identified as being born to a father born in Kentucky.Were they born of another man, or an enumerator mistake?Could this tie into the story of his visiting his grandmother "Tackett"?Or was this person the mother of Caroline Wright, (see 1880).
The 1880 Census for Saylor, Polk County, Iowa
James Wright, age 62, physician and farmer born in Kentucky
Caroline, 47, housekeeper, bon in Indiana
Alonzo B, 27, R.R. Engineer
James A, 23, student at law
Charlie E, 16, at school
Nellie May 11
Ida Belle 5.
The 1870 Census for Lee, Polk County, Iowa
James 52, farmer, born in Kentucky
Caroline, 37, born in Indiana
James A 13
Charles E 6
Nella May 1.
In 1900, Alonzo Wright was in Crow Creek, Weld Co, Colorado, working as a servant/farm laborer in the home of Herbert Russell.He was single and 46.
In 1900, in Pocatello, Idaho, there is a Charles E. Wright, born in Iowa to both parents born in Indiana (Of the Charles Wrights, 12 of them) born 2 years plus/minus of 1864, he is the only one to have Indiana for a mother birth place).Born January 1864.newspaper editor.Married to Susan M, born Oct 1864 in Iowa for 13 years, no children.Sister-in-law, Grace Horn born Mar 1880 living with them.
---In 1910, Charles E and Susan are now living in Monpelier, Bear Lake County, Idaho.Mother Caroline, widow, age 78 now living with them.She was mother of 9, 2 living.(Charles and James ?).A 12 year old nephew Eyartt? Herman? is also in the home.
While this may give you some proof as to grandfather being on the railroad and some other family background, it does not answer the question of who painted the picture.There doesn't seem to be any D. Wright in the immediate family or close cousins.It does appear to be possible that James D was not the son of James A.
I asked a lot of questions in this, I don't need to know the answers, just questions you could mull over for clues.