Pre-Columbian (30)
http://www.worldheritagesite.org/categories/category29.html

Cahokia
Calakmul
Caral
Chaco
Chan Chan
Chavin
Chichen-Itza
Copan
Samaipata
El Tajin
Head-Smashed-In
Joya del Ceren
Machu picchu
Mesa Verde
Monte Alban
Palenque
Paquime
Poverty Point
Quirigua
Rio Abiseo
San Agustin
SGang Gwaay
Diquis
Taos Pueblo
Teotihuacan
Tierradentro
Tikal
Tiwanaco
Uxmal
Xochicalco

I would also add Yagul and Mitla

I suppose we can't have them all? Difficult to choose, I like these.

My choices:

Cahokia - The most important Precolumbian site north of Mexico, however, it is little excavated. I don't think it should have received its status the way it is (similar reasons led to deferral in Guayalbo). N
Calakmul - A significant Maya sites, very well maintained, but there are so many. A maybe?
Caral - The oldest city in the Americas. Y
Chaco - One of three sites in the US representing the Pueblo culture. Not the best one. N
Chan Chan - The largest adobe city in the world, one of the most significant Preincan sites. Y
Chavin - Yet another significant Preincan site. Different from Chan Chan and Caral it is set in the Andes. Y
Chichen-Itza - Perhaps the best known Mayan site. Y
Copan - Another of the most major Mayan sites. Y
Samaipata - A bit of a nice. N
El Tajin - Most significant Totonac building, but still probably a N
Head-Smashed-In - Significant for representing hunting techniques. Y
Joya del Ceren - Interesting, but not as important as other Mayan sites. N
Machu picchu - iconic Y
Mesa Verde - interesting for its cave dwelling, but I am not sure it is important enough. Maybe
Monte Alban - The most significant Zapotec site. Y
Palenque - perhaps less important Maybe
Paquime - not significant enough N
Poverty Point - perhaps better suited to represent the Mississipi culture that Cahokia. Additionally important representation of a hunter-gatherer society. Y
Quirigua - Less significant N
Rio Abiseo - Gran Pajaten represents the otherwise unrepresented Chachapoyas culture which was a major culture in the tropics. TWHS Kuelap would be a better representation, but in its absence I would give it a Y
San Agustin - For its beautiful giant sculptures Y
SGang Gwaay - The only holy site still in use by the original population. Y
Diquis - Too specific and insignificant N
Taos Pueblo - The only residence still in use (outside Cuzco which is not in this category). Y
Teotihuacan - The most significant city in the Aztec realm after Tenochtitlan (Mexico City), but it is older. Y
Tierradentro - The most interesting burial site. Y
Tikal - Again one of the most significant Mayan sites. Y
Tiwanaco - Another major Preincan cultural centre. Y
Uxmal - not significant enough N
Xochicalco - not significant enough N

I would also add Yagul and Mitla - For Mitla, the Zapotec site: the culture is already better represented by Monte Alban. N

My selection:

Chichen Itza
Macchu Picchu
Palenque
Tikal
Uxmal (for the intricate Mayan carvings)
Mesa verde
Chan chan

My selection:

Chan Chan
Chichen-Itza
Machu picchu
Mesa Verde
San Agustin
Teotihuacan
Tikal

Chaco - Not as iconic as Mesa Verde, but probably more important. Y
Chan Chan - Clearly one of the most significant Pre-Incan Civilizations. Y
Chichen-Itza - Icon and representative site of of Mayan civilization. Y
Copan - Icon and representative site of of Mayan civilization. Y
Machu Picchu - World class, perhaps most important and iconic Pre-Columbian site. Y
Mesa Verde - Cliff Palace, Balcony House, and unique adaptation to a harsh environment make Mesa Verde exceptional. Y
Poverty Point - Largest concentration of hunter-gathers in the world. Y
SGang Gwaay - In a state of arrested decay, authentic and perhaps the most important North American site outside the American Southwest. Y
Taos Pueblo - The oldest continually inhabited village/town in the United States. Y
Teotihuacan - Third largest pyramid in the world. Y
Tierradentro - The area holds the largest concentration of Pre-Columbian monumental burials. Y
Tikal - Icon and representative site of of Mayan civilization. Y

Caral
Chan Chan
Chavin
Chichen-Itza
Machu picchu
Mesa Verde
Monte Alban
Palenque
Tikal
Tiwanaco
Teotihuacan

I'm pretty much in agreement with all of Assif's recommendations apart from this one. Much to my surprise when I visited, I think this is actually a really impressive site and probably was the best of the Pueblan places, it isn't as Iconic as Mesa Verde, nor still inhabited like the Taos, but the quality was brilliant, shame it isn't as well known.

The list of this category is really great! But I think 3 sites for Pueblo culture, Chaco/Taos/Mesa Verde, are too much better choose one, and my opinion is Mesa Verde for its more complete archaeological findings on ancient people's agricultural, irrigation and architecture.

"Chaco hosts the densest and most exceptional concentration of pueblos in the American Southwest." - wiki

"Chacoan developers assembled 15 major complexes which remained the largest buildings in North America until the 19th century." - wiki

It was a significant trading center with a large population. This network of roads and connected components allowed contact with peoples along the coast of California and as far South as Mexico City. Mesa Verde is indeed spectacular, but its difficult to argue its importance compared to Chaco.

For myself its very hard to select one (maybe 2) of these sites: Mesa Verde, Chaco, and Taos. Thats because they are actually very different and taken together tell a far more complete story. Let's also be honest, there are likely 3-5 additional Southwest Puebloan (Sinagua/Hohokam) sites worthy of inscription. If I had to select only (2), I would grudgingly go with Mesa Verde (Iconic) and Chaco (Massive complex and for importance), though its a shame to leave out Taos Pueblo which is unique and special for its own reasons.

As I said I especially like this category, so it is difficult to leave some out.

My choice for the A-list:
- Caral Supe: it's remote, it's a mystery, it's great
- Chaco Culture - impressive remains and rock art of the Anasazi
- Chichen-Itza: greatest Maya-site
- Machu picchu: greatest Inca-site
- San Agustin: for its megalithic sculptures
- Teotihuacan: for its huge pyramids
- Tikal: no.1 Maya-site in jungle setting

There are some categories which should shed rather more than their 60% and some rather less - I think this one is in the latter group. Its "extra" can be "paid for" by e.g Maritime!! Els's 7 are all worth having but represent too harsh a culling and exclude some important sites which are, IMO, the equal of sites already left in under other categories and which are "required" to ensure a better coverage of this domain. So I am rather more with Assif and Meltwaterfalls with their 16/17 "Y's". I have visited 18 of the 30 but I am not sure that my visit experience has made much difference to my choices.

First the ones I regard as clear decisions -
-Calakmul - No as per others. Not outstanding enough to justify yet another Mayan site
-Caral Y - as per most others!
-Chan Chan - Y to cover the Chimu and for its size and "mystery". Can this site really be left out ?
-Chichen-Itza - Y as per others
-Copan - No as per others
-Samaipata - No -as per others
-Joya del Ceren - No as per others
-Machu picchu - Y as per others
-Palenque - No - OK very fine but can Maya have more than 2? Tikal will have to represent the Jungle sites
-Paquime - No -as per others
-Poverty Point - No -as per others
-Quirigua - No as per others
-SGang Gwaay - Y. I really do think we need a NW site
-Diquis - No - as per others
-Teotihuacan - Y -as per others
-Tikal -Y - as per others
-Uxmal - No -as per most others. OK nice carving but can Maya really have more than 2?
-Xochicalco - No as per others

So - of these "easy 18" Y = 7 and N = 11
Which leaves the "difficult 12"!
3 "Pueblo related"
-Chaco
-Taos
-Mesa Verde
Well, definitely only one of these. Each has its merits and covers slightly different aspects but, having visited all 3, I come down in favour of Chaco for the extent of its ruins and obvious significance.

We have covered above a lot of the better known Pre-Columbian civilisations and the remaining 9 sites cover some less known ones or ones which are perhaps a bit similar to what has already been recognised. I am torn as to how small to grind on trying to represent yet more different "civilisations" and architectural periods/styles. If these were European sites we would happily say that both (E.g) Romanesque and Gothic should be given at least one representative!! Or that a Viking and a Norman site each justify inclusion! How do we enrue that we apply the same degree of differentiation here?

-Cahokia – The only Mississippean site, "most important pre-Colombian site N of Maxico".I note Assif's concern about lack of excavation but still feel it needs to be included. Y
-Chavin - 1500 to 300BC. Precedes Nazca and Tiwanaku. MAYBE
-El Tajin. Have been there and it is a great site to visit. Wiki says "one of the largest and most important cities of the classic era of Meso-america. A part of the Classic Veracruz culture, El Tajín flourished from 600 to 1200 C.E.". We have Teotihuacan and Tikal (and possibly Monte Alban) from the Classical era but each represents a different culture as does this. But do we need yet another site of "Pyramids"? But it is a wonderful site to visit and the "Pyramid of the Niches" is rather special. So Y

-Head Smashed in. Although there isn't a lot to see I think this site is different enough and represents the way of life of the Plains buffalo hunting "Indians" . So Y
-Rio Abiseo – I fear this site will suffer because it is so little known and because its archaeological site (Gran Pajetan) is hidden behind its Natural values (which themselves aren't enough?) . It just doesn't seem important enough. So N
-San Agustin /Tierradentro both in Colombia, both "Burial related" but, apart from that, both very different? How on earth to distinguish? Whilst both are very interesting sites with fine remains my feeling is that both are too much "outside" the "mainstream" of South American pre-Colombian remains – MAYBE
-Monte Alban/Oaxaca – I bit of a shame that Oaxaca is included. We have enough Colonial cities don't we? As Middle pre-classic it is one of the earliest Meso American cities. MAYBE
-Tiwanako – Has that "Gate of the Sun" and covers a major culture spreading across 300BC – 300AD pre Chimu and Inca and post Nazca. So – MAYBE

So
Y = 11 (Caral, Chanchan, Chichen, Macchu, Sgang, Teotihuacan, Tikal, Chaco, Cahokia, Tajin, Head Smashed)
N = 14
Maybe = 5 (Chavin, Tiwanaku, Monte Alban, San Agustin, Tierradentro). I think we need more discussion about how best to handle all these different periods and cultures in the Americas. My feeling is that Zapotec (Mte Alban), Chavin and Tiwanaku are important enough civilisations and sites to have their sites included if there is room.b I just don't know about the 2 Colombian ones!

Summarizing:

Cahokia
Calakmul
Caral - oldest city in the Americas
Chaco - impressive remains and rock art of the Anasazi
Chan Chan - to cover the Chimu and for its size and "mystery"
Chavin - 1500 to 300BC, precedes Nazca and Tiwanaku
Chichen-Itza - Icon and representative site of of Mayan civilization
Copan - representative site of of Mayan civilization
Samaipata
El Tajin
Head-Smashed-In (already in on different category (Agriculture))
Joya del Ceren
Machu picchu - representing the Inca civilization; perhaps most important and iconic Pre-Columbian site
Mesa Verde - Cliff Palace, Balcony House, and unique adaptation to a harsh environment
Monte Alban - most significant Zapotec site
Palenque
Paquime
Poverty Point - to represent the Mississipi culture, important representation of a hunter-gatherer society
Quirigua
Rio Abiseo
San Agustin - for its beautiful giant sculptures
SGang Gwaay
Diquis
Taos Pueblo - oldest continually inhabited village/town in the United States
Teotihuacan - for its huge pyramids
Tierradentro - holds the largest concentration of Pre-Columbian monumental burials
Tikal - no.1 Maya-site in jungle setting
Tiwanaco - covers a major culture spreading across 300BC – 300AD
Uxmal
Xochicalco

Hi Els,
I appreciate that it is a very difficult task to summarise and draw conclusions from a somewhat incompatible set of assertions and arguments - but what criteria are you using to decide whether a site is bold or italic?
Is 1 Y not enough to get an italic? I look at Cahokia and Tajin above - both recorded as N but each receiving some support!

As far as I understand, no it isn't. For an italic you need two Y supporting it. Otherwise, we would have very little clear No's. I guess that about half of the No's got at least one member suggesting them.