today we're at petroglif national monument, specifically at the vlg's day use area. the vlog's day use area provides trails to five vlogs and it looks out over the city of albuquerque out towards the sand ya mountains. the petro glyph tells the story. hot molten lava poured out in a series of six vloggic eruptions, some spreading a couple of miles to the east. as these eruptions took place, they flowed out over layers of soil that was here in the rio grande valley. as these layers hardened, they hardened into a 17-mile long

area of black assault boulders on which we've got 24,000 petroglyphs. the story of the national monument isn't just about a single petroglyph or concentrations. it also includes the volcanic cones and the mesa top that spreads out towards albuquerque. the pueblo people would come up to the mesa top. we have evidence of them carrying water and farming. sometimes they would send their children up here to keep the rabbits away from their crops. we see many ancient trails up here and this becomes part of a larger spiritual landscape that's important to most pueblo people. we're here at boca negra canyon and we're going to be walking on the macaw trail.

what we see here is 113 feet tall. these black boulders once came from several sheet flows from if the volcano. most of our 150,000 visitors stop here first. this is one of the first petroglyph that people who come to the monument might see. it is a carving on to the rock. pueblo people would use stone chisels and hammered to peck, abrade, incise and carve out the rock. sometimes people ask us how these were discovered. but for pueblo indians they are as old as time. they've known about them since their creation stories. modern day archaeologists date most of these images from about

1200 to 1650. a few are older, those which are done by early spanish sheep herders who were out here as part of the land grants. in the 1970s archaeologists came out to the west mesa and began to inventory these images. later interest grew and eventually it became a national monument. to the pueblo people they believe that the petroglyphs choose when and to whom to reveal themselves. sometimes tls the shadow, or sometimes it is the glare or sometimes it is the attitude and sensitivity with which we look at these images that reveal themselves. sometimes telling the people not to touch them is not enough. we know that nobody should shut the petroglyphs but we do give people an artificial bolder we have created for such purpose so we get the touching out of the way. we want people to understand

that these are sacred images and they continue to be important to the pueblo people. eventually over time, a patina will form an that's what's meant to happen. but until then, we ask people not to touch these images. petroglyph national monument is one of the few park units owned and pratd not solely by the national park service. petroglyph national monument is managed by the city of albuquerque and the national park service, and we work together with the city to help protect and preserve these resources for the future. in the last 20 years we've had several challenges. land acquisition. being everything for everybody. the creation of trails. vandalism. the construction of roads through the monument. the expansion of a general aviation airport. but probably our biggest challenge is storm water runoff from upstream suburban development. because we are completely surrounded by the city of albuquerque. as you walk the trails of

petroglyph national monument and look out, you might notice large concentrations black boulders and that's where we often see concentrations of petroglyphs. we are in the heart of this canyon where this is a dense concentration of petroglyphs. we have documented over 20,000 within the monument boundary. this canyon is home to 5,000 of them. we see an animal over here. we are not really sure what it means. something that looks like a sheep brand. it may be a cross. thoet might have been carved by early spanish sheep herders. i see something that looks like a bird and some unidentified animals up on that rock. here we see a concentration of boulders with many hand images of different sizes. some of which have an additional appenda appendage. the pueblo people believe if a

child is born missing a finger or with an additional toe, that that's a sign of power. with a concentration of hand images here, we have to wonder why. maybe it is because people passed through this way. maybe this is a type of a calendar. we don't really know. only the people who carve these images know for sure. what we do know is if we followed the aroyo from the heart of the canyon, we would end up in the pueblo, an 1,100 room adoe by multiple plaza structure located on the rio grande. and it was important to them because of the location to the petroglyphs. the high peaks where mother earth meets father sky. they would come up here, follow spirit ways, they would say prayers, they would make offerings, and they would carve images in to the rock. sometimes it is a form of

passageway or a map. others might be a counting mechanism or clan image. but to many pueblo people, they say the spirits would leave this world and go on to the next world through these petroglyph images. the pueblo people call this place the place that people speak about. plongs belongs to all of us. all americans. not just today, but future generations. it is a place of respect. it is a place of solitude. it is a place of wonder. american history tv is marking the centennial of the national park service. we asked members of congress which national park service site in your state has special meaning to you and why. >> oregon has so many special places. for example, haystack rock on the oregon coast. where my wife and i were married

is a treasure to us. and i think from the standpoint of parks, i mentioned crater lake national park. this is a real treasure and it is enjoyed by not just people from the united states, but all over the world. it's 14 years older than the park service itself. and the water is absolutely incomparable. it's just surrounded by spectacular recreation and wilderness. this is a place like no other. the solitude, for example, is something that is treasured by all. in fact, couple years ago there was an effort to fly helicopters over crater lake and i stepped in and blocked it because the citizen outcry to helicopters was so great. i also believe that as we protect our parks and celebrate this birthday, we recognize that

recreation and tourism is a huge economic engine for our country. it produces, for example, at crater lake $61 million worth of revenue every single year. i just look forward to celebrating with friends and neighbors and guests from all over the world. because this will be a very special time at a very special place to recognize what is best about our country. this, of course, is the big party. the 100th anniversary. and it is because we've said in our country that our parks are special places. i was especially struck during the government shutdown when there was a debate about the services that were most important to americans. and our people said just don't mess with america's special places. >> join american history tv

tonight live at 7:00 p.m. eastern time to commemorate the national park service centennial. 100 years ago president woodrow wilson signed the bill creating the narc park service. today we look at these national and historic treasures. at 7:00 p.m. eastern we're live from the national park service's most visited historic home, arlington house, the robert e. lee memorial the a arlington national cemetery. join us with your phone calls as we talk with robert stanton, former national park service director, and brandon bice,

overs overseer. live from arlington house at 7:00 p.m. eastern on american history tv on c-span3. [ speaking foreign language ] want to welcome you all to

castillo dos marcos. the fortress behind you is the fourth fortification to bear this maim but it is the first one to be made out of stone at st. augustine and it was built for a particular reason. spain decided they had to build a stone fortification in st. augustine to ensure their foothold on the florida terth. they were concerned about england encroaching and pushing them out of the area and they saw florida as very important in helping to defend their hold on the caribbean and central and south america. they start construction in 16 72, complete it in 1695. you got 23 years worth of construction. the biggest reason for all that time only about 175 people working on the project at any one time. all the stone had to be quarried from over on the island across the bay, barged across. no mechanical stuff, no metal banks. it db barges. it is allan