According to [Richard] Hardorff, Blue Horse was born about 1821.

Blue Horse in 1872:

Photo by Alexander Gardner (SIRIS) — Dietmar Schulte-Möhring

I've found the reference about Blue Horse and Red Cloud being born on the same year and day (see http://www.harvard-diggins.org/Burbank/Years/1910/1910_HI_Chief_Blue_Horse.htm) but I still lack any info about his death date.

I've three pictures of him as an old man:

The Heyn one:

Another one taken in 1900:

And an Edward Curtis one (1907):

All I know then is that he was still around by 1907.

And this is the one taken at the 1901 Pan-Am in Buffalo, New York:

Left to right: F. T. Cummings, High Hawk, Jack Red Cloud, Blue Horse, Little Wound, William Jennings Bryan — jinlian

Isn't this Blue Horse in the front row of this group? And isn't that an older Red Shirt at the right of the back row?

— Grahame Wood

The third man on the left (first row) in your first photo is just Blue Horse! I suppose it was taken at another exposition - Omaha 1898, maybe? — jinlian

Shot-in-the-Eye is standing far left in the back row, and Painted Horse stands left of Red Shirt, I think.
— Dietmar Schulte-Möhring

On a vaguely related note, was the Blue Horse that travelled with Cody in 1887-8 actually a Shoshone? Seeing this thread reminded me that I'd read somewhere that Cody would pass off some of his Lakota as members of other tribes for "dramatic" purposes.

Anyhow, for completists' sake, here is THAT Blue Horse:

— Grahame Wood

I think the man in the cabinet card you've posted is definitely Blue Horse the Shoshone. Being born in 1821 or 1822, our Oglala Blue Horse would have been about 65 at the time. — jinlian

I think what Grahame means is that this Blue Horse could be a son or nephew of our Blue Horse. From the way he looks I would say he could very well be a Lakota ... or perhaps the Shoshone changed their hairstyle during this period to attract Cody's audience. — Dietmar Schulte-Möhring

Well, it was partly due to shows such as the Wild West that the Lakota paraphernalia became essential in the representation of the "traditional" Indian. The necklace and the breastplate worn by the Indian in the picture are definitely Lakota, but unfortunately this doesn't help much with the identification, as we're speaking about an "actor." On the other hand, changes of hairstyle were quite common among native tribes: I think for instance of the Pawnee hairstyle, or even the Crow, whose peculiar pompadour was adopted quite late (since the 1840s).

I've checked Mike Stevens' tiyospaye website and it reports that there was in fact another Blue Horse, son of Stands Good, born in 1869. According to the same website, our Blue Horse, the Wagluhe, had a son called Little Medicine, born in 1867. Anyway, I think it's possible that Blue Horse had more children than those reported there and that one of them toured with Cody: Stevens's records are based on census data which aren't 100% accurate.

Here are the last two images of Blue Horse have in my collection:

Blue Horse's Portrait by E. Burbank

A detail to make identification easier: Blue Horse lost his right eye sometime between 1880 and 1895. — jinlian

Blue Horse (M)
(1820-), #16477 — Blue Horse – Oglala – 1872 Blue Horse was born in 1820; SHON-KEE-TOH.
He witnessed the meeting of Chief Dull Knife; The Treaty of Fort Laramie was an agreement between the United States and the Lakota nation, signed in 1868 at Fort Laramie in the Wyoming Territory, guaranteeing to the Lakota ownership of the Black Hills, and further land and hunting rights in South Dakota, Wyoming, and Montana. The Powder River Country was to be henceforth closed to all whites. The treaty ended Red Cloud's War. The treaty included articles intended to "insure the civilisation" of the Lakota; financial incentives for them to farm land and become competitive - and stipulations that minors should be provided with an "English education" at a "mission building". To this end the US government included in the treaty that white teachers, blacksmiths and a farmer, a miller, a carpenter, an engineer and a government agent should take up residence within the reservation. Repeated violations of the otherwise exclusive rights to the land by gold prospectors led to the Black Hills War.

http://www.pbs.org/weta/thewest/resources/archives/four/ftlaram.htm.

Blue Horse was listed as Head of the Household on the Indian Census at Pine Ridge Indian Reservation, Dakota Territory, USA, in 1886. Blue horse was listed as Head of the Household on the Indian Census at Pine Ridge Indian Reservation, Wakpamini District, Shannon Co., Dakota Territory, USA, on June 30, 1904.

Council Fire Woman (F)
(1830-),#16478 — Council Fire Woman was also known as Peta Ominiciye.
She was born in 1830. She was listed as Blue Horse's wife in a census in 1886 at Pine Ridge Indian Reservation, Dakota Territory, USA. She was listed as Blue Horse's wife in a census on June 30, 1904 at Pine Ridge Indian Reservation, Wakpamini District, Shannon Co., Dakota Territory, USA.

Little Medicine (M)
(1867-), #19274
Little Medicine was born in 1867. He was the son of Blue Horse and Council Fire. Blue Horse was listed in the Indian Census on the date of in 1886 at Pine Ridge Indian Reservation, Dakota Territory, USA; Blue Horse is listed as 67 on this Census. His Wife Council Fire was listed as 55 years old.

Jennie Blue Horse (F)
(1873-), #19275
Jennie Blue Horse was born in 1873. She was the daughter of Blue Horse and Council Fire. Blue Horse was listed in the Indian Census on the date of in 1886 at Pine Ridge Indian Reservation, Dakota Territory, USA; Blue Horse is listed as 67 on this Census. His Wife Council Fire was listed as 55 years old.

Lizzie Blue Horse (F)
(1874-), #1927
Lizzie Blue Horse was born in 1874. She was the daughter of Blue Horse and Council Fire.

— LaDonna Brave Bull Allard

In 1869 Spotted Tail killed Blue Horse's brother Big Mouth at Whetstone agency. Here is a newspaper sketch of that incident:

There was a photograph taken of Big Mouth and his brother Blue Horse among others by photographer Ridgway Glover at Fort Laramie in 1866. Unfortunately Glover got killed and his photographs are lost in mystery.
— Dietmar Schulte-Möhring

The sketch of the Big Mouth assassination shows however a surprisingly accurate portrait of Spotted Tail, even more striking when we think of some caricatures featuring in the contemporary illustrated press. I suppose the fact that pictures of Spotted Tail circulated widely helped too.

On the other hand, I've always found amazing the strong resemblance between Blue Horse and Red Cloud. They were first cousins, but they certainly looked as if they were twins! — jinlian

Blue Horse died in the Wakpamni District on the Pine Ridge Reservation on July 16, 1909. — Ephriam Dickson

George Hyde stated that Blue Horse (Sunkawakan To) and his brother Big Mouth (I Tanka) belonged, in origin, to Itesica band (the same of Red Cloud). Later (I think by marriage) he became a Wagluhe (Loafers), a band that generally camped around Fort Laramie (Wyoming). He was born in 1821. — Charlie

Here's another of the four portraits of Blue Horse by Elbridge A. Burbank: