I just noticed that there has been a name change to this WHS before 2000: from Head-Smashed-In Bison Jump at inscription to Buffalo Jump.

Anyone knows when that happened? Found nothing on the Unesco site page

Interesting! There is certainly NO mention that I can find (either on UNESCO or even on the Web) of the change in name before the 2000 change which merely removed the word "complex" from the name both in French and English -and the name from which it was removed is clearly given as "Buffalo Jump" in English! So, some time between its inscription in 1981 and the "second" name change in 2000 there must have been an earlier name change -either de facto or de jure from "Bison Jump" to "Buffalo Jump" in English.

Of course in French it is still (as it has been since 1981) "Precipice a Bisons"!!
We were there in 1990 and the title of the place as on the Visitor Centre signage (opened 1987) was certainly "Buffalo Jump" back then. It is interesting to note that the map from the original nomination (no nomination file available) shows various "Buffalo Jumps" - including that of "Head-Smashed-In". The phrase "Bison Jump" ONLY appears in the AB evaluation (and was then carried through to the Inscription). I wonder if it was done originally in French and "translated" to English by someone who insisted on the scientific correctness of the word "Bison" over "Buffalo"!!

I don't think that there is such a thing as a "Bison Jump". In Canadian English it is and always has been a "Buffalo jump". The creatures which jumped over it were (American) "Buffalo" whose correct scientific name was/is "Bison bison" and which are called (more correctly) "Bison" in French. It is interesting to read the 1804 Journals of Lewis (of Lewis and Clark) describing "Buffalow" being chased over a precipice. All the other "Jumps" I can see described in Wiki are "Buffalo Jumps" (Vore, Ulm Pishkun, Madison, Big Goose Creek etc).

So quite why Canada, and particularly Alberta, acquiesced in the site being given IN ENGLISH the name of "Bison Jump" when that wasn't what it was called locally I don't know!! The site is located in the Piegan Reserve and the Blackfoot word for a Buffalo Jump was apparently a "Pishkun" - so one might have expected Canada to adopt a native language word when changing names - but perhaps 3 titles for 3 different languages was too much!.

First Peoples Buffalo Jump State Park is around 200 miles southeast of its Canadian counterpart and was known by "The former name of the park was derived from the Blackfeet word "Pis'kun," meaning "deep kettle of blood," and the nearby town of Ulm".

Perhaps this explains the name confusion over the years, and why the Canadian site might be hesitant to use a Native name of a site relatively nearby in Montana that used to go by that name (or similar).

Interestingly enough, the Montana site just became a National Historic Landmark this week, and now officially has national protection. Perhaps a worthy extension? Indeed, the size, age, and fossils seems to be fairly comparable between the 2 sites. On a side note, I see Lewis & Clark were mentioned by Solivagant, interestingly the site(s) he described are sites found in Montana, not Canada.

The criteria for inscription for the Canadian site starts with, "Head-Smashed-In Buffalo Jump is one of the oldest, most extensive, and best preserved sites..."

Now I know why they said "one of the".

I guess that shows the benefits of getting in early and playing the game.

Does this work in a similar way to the WHL with nominations and additions each year, or is it more a ad hoc process of certain sites getting inscribed when circumstances are right?

The Wiki article on the scheme is quite good
"The National Historic Landmarks Program relies on suggestions for new designations from the National Park Service, which also assists in maintaining the landmarks. A friends' group of owners and managers, the National Historic Landmark Stewards Association, works to preserve, protect and promote National Historic Landmarks."
and
"NHLs are designated by the United States Secretary of the Interior"
and
"If not already listed on the National Register of Historic Places, an NHL is automatically added to the Register upon designation. About three percent of Register listings are NHLs"
See http://en.wikipedia.org/wiki/National_Historic_Landmark

Yes, each site has to be nominated. All 10 of the Frank Lloyd Wright buildings nominated for 2016 are NHL, some only recently so. The NHL Spring Meeting 2015 just occurred, there is a Spring/Fall meeting every year. It many ways it operates like a smaller version of the WHL. Sites. Historic sites are even removed, expanded, and if a structure is "in danger" NHL listing might be seriously considered by those seeking to preserve the site.

Thanks for the feedback, although I fear I am about to loose some time seeing how many of the sites on that list I have visited!

===From looking into that list I've already learnt something, there was a real politician from New Hampshire called Josiah Bartlett, I thought someone had been playing a trick on the wikipedia article :)===