attorney, which led to being head of the criminal division in washington, which led to being elected governor of massachusetts. >> have i forgotten or been unable to elicit any stories that you would like -- >> that's a wrap. >> governor, ambassador, thank you. it's been a pleasure. >> thank you. [captioning performed by the national captioning institute, which is responsible for its caption content and accuracy. visit ncicap.org] [captions copyright national cable satellite corp. 2019] announcer: is the impeachment inquiry continues, we look back to watergate and the impeachment of richard nixon. for more interviews with plea -- key players and discussions on the process, this is sees been.org/history and search nixon impeachment. our c-span city tour takes american history on the road to feature the history of the cities across the country.

here is the recent program. amy: montana is a wonderful place for discovery of dinosaur fossils not only because of the rocks we have and are present in the state but also because they are exposed. in almost the entire eastern portion of the state is exposed rock from the cretaceous time, which preserved a lot of dinosaurs. the most famous formation for dinosaurs preserves the last of the dinosaurs before they became extinct at the end of the mesozoic era. we have a lot of formation here in the state and that is where we go to find triceratops and t-rex. two of so two of the most iconic are here and a tan.

-- in montana. the first discovery of fossils in montana go back to the native american days. these bones have been eroding out of these areas forever. case were discovered at the turn of the century in the late late 1900s -- late 1800s. a lot of those fossils went back to the east coast to large institutions like the carnegie or the smithsonian. it wasn't until the late 70's that we found a site thanks to land owners that were rock hounds when a family found these fragments of baby dinosaur bones and dinosaur eggs. not just babies but also nestlings that have been clearly

cared for. likeinosaurs were alligators, so they would lay them and then be gone and not be present to raise them. this changed what we thought about dinosaur behavior. it put this museum on the map. this hall is called the hall of horns and teeth. from focused on fossils the hell creek formation. the formation is famous because of two types of dinosaurs in particular. that is triceratops, which is the horned dinosaur. that is where we get the hall of horns. then the teeth come from t-rex. the formation has produced a number of phenomenal

tyrannosaurus rex specimens. t-rex is full of teeth and quite the fearsome predator. the dinosaur behind me does have a name. its official specimen number is here. the t rex was discovered on the fourth of july in the late 90's. if someone asked me, why were you working on the fourth of july, i say, why would you say this is work. this is fun. it was local ranchers who found montana's t-rex. the skeleton behind me here is 60% real bone.

it is very rare to find a t-rex or any dinosaur that is 100% complete. i don't think any of us would be complete after 66 million years of being in the ground, to have a dinosaur that is 60% real fossil bones standing in front of you, really a rare and spectacular opportunity. behind me as well you can probably see the horns of the triceratops we have mounted as well. it is known for its iconic three horns. it had to above the eye and a smaller one on the nose. it was likely to be a

favorite prey item of t-rex. it was a vegetarian dinosaur that would have been looking out and trying to avoid t-rex as much as possible. that's why this crazy horn ornamentation came from. right behind me is a triceratops growth theory. they are called triceratops because they have two horns about their eyes and one above their nose. it is also one of the most commonly found dinosaur in the formation. when

we look at food chains, there are a lot more herbivores in the ecosystem than top predators. we find a lot more triceratops bones than we do t-rex bones. here you can see a great sample. the benefit of being such a commonly found dinosaurs we can see a lot about how triceratops grew and developed throughout its life. you can see one of the smallest triceratops skull. as we continue down the growth series, we start to see some fangs change. we start to see those horns above the eyes get bigger. and through their life and as they

grow, these areas fused later and later. thesen see that in teenagers, these are more fused. horns are bigger and more curved. we continue on through getting closer to -- closer and closer to adulthood. these were not fully mature yet. there we see the largest of our two. some paleontologists believe that this change would have to do with species recognition. our largest of the triceratops also has the biggest curved but downward curve horns, and what we see are these holes

that develop. these holes would not have been holes in life. it would have been covered with the skin. here whontologists study triceratops leave the bone may have been deposited on these bigger horns on their facial region. how we know about all of these things, that this is an older triceratops and not a different species, is because of bone histology, and using histology to tell the age of individuals. histology is when you slice up an animal bone, and you slice it so thin that you can then put it on a slide and look at it under a microscope

and look at the microscopic level of that bone and see things like cellular development that to give us an idea of the ages of these long extinct giants. not only do we have a a triceratops growth series, that we also have the largest t-rex growth series here. that is what you see here. skulln see the smallest to have ever been discovered. this is a print out of it. this is from montana. then we have another juvenile and younger t-rex. this one is also a replica. those are your younger ones that in that world there has been debate about whether or not that represents a

different species or if it is just a juvenile t-rex. here through the study, we are confident with our hypothesis that these are juveniles. this specimen, this rex, and this is an incredible story largely due to , the research of dr. mary schweitzer, a research associate here at the museum of the rockies. her research found the oldest traces of soft tissue to be preserved in the fossil. an incredibly scientific specimen that has changed what we know about dinosaur soft tissue and dinosaur biology. largersee larger and t-rex. this is the skull of the

montana t-rex to see up close and personal. our second largest, our second oldest is going to be mor-555. this is the centerpiece of the smithsonian's deep time exhibit. and then the largest of our t-rex growth series is one of the largest t-rex goals to be discovered ever. it is more than five feet in length and would have been huge. it is much larger than the skull of montana's t-rex. the rest of the skeleton would have

been much larger than what you see here on display. very few museums have an opportunity to see so many actual t-rex specimens in one exhibit. that is one of the highlights of coming to the museum of the rockies. here we are at the bowman dinosaur viewing laboratory. this gives visitors an opportunity to see paleontologists work on fossils right in front of them. our volunteers can explain to visitors how we find fossils in the field, how we get them out of the field, how we give them -- get them back to the museum. then we cleaned them up they can

go on display. you can see a variety of different dinosaur bones that are being prepared here in view for our visitors to see. here is the triceratops femur still in the works. it needs to be consolidated. it still in its field jacket, which is made out of plaster and burlap. next to it we have a triceratops vertebra. this is an individual backbone. it is fairly well together, but it looks like some of the spines need to be glued back together as well. we have additional vertebra from triceratops as well as other material. we have one of our

volunteers. levi, how long have you been a volunteer here? six years. how many hours? over 5000 hours have volunteered and donated to be here in the viewing lab. these are actually the teeth they grow in a dental battery. levi is very skilled at putting this back together. it is a lot of work and we want to show how proud we are of our all in tears and how proud we are to share the process of paleontology with our visitors. i think it's extremely important to have small regional museums

as opposed to the large one. i think that are extremely important also. they preserve history of our nation. but it is extremely important to have these local museums such as museum of the rockies to give back to our communities. it brings montana to the world in the world to montana. announcer: join us on book tv, and american history tv as that city tour explores the american story. and watch videos from all of the toy we visit, go c-span.org/city tour and follow us on twitter at c-span cities. the student cam competition is in full wing. it'll and high school students are hard at work on their short theyentaries on the issues

would most like presidential candidates to address. we would love to see your progress share your photos and take us behind the scenes. for a chance to win additional cash prizes, still working on an idea, we have resources to help out. our getting started page at student cam.org with information to guide you through the process. $100,000ll award including a $5,000 grant, all agile -- entries must be uploaded and received by midnight on january 20, 2020. deck of the best advice i can give is not to be afraid to take your issue seriously. you're never too young for an opinion. so let your voice be heard. announcer: or more information, go to our website. next, on the presidency, matthew costello talked about his new

book "the property of the nation: george washington's tomb, mount vernon, and the memory of the first president." hey talks about how this helped historical narrative of the first president. he is a historian at the white house historical association west -- which hosted this event. >> good evening everyone. the house historical association, i would like to welcome our friends joining us by c-span and those who are here with us tonight who are the really smart people in washington, d.c., because you have chosen to be here above the nationals' baseball game and above the televised presidential debate tonight. we think we have got the best thing going here and we are glad you chose to be with