Information:  - The American Revolution was a political upheaval that took place between 1765 and 1783 during which colonists in the Thirteen American Colonies rejected the British monarchy and aristocracy, overthrew the authority of Great Britain, and founded the United States of America.  - Canada (French: ) is a country in the northern half of North America. Its ten provinces and three territories extend from the Atlantic to the Pacific and northward into the Arctic Ocean, covering , making it the world's second-largest country by total area and the fourth-largest country by land area. Canada's border with the United States is the world's longest land border. The majority of the country has a cold or severely cold winter climate, but southerly areas are warm in summer. Canada is sparsely populated, the majority of its land territory being dominated by forest and tundra and the Rocky Mountains. About four-fifths of the country's population of 36 million people is urbanized and live near the southern border. Its capital is Ottawa, its largest city is Toronto; other major urban areas include Montreal, Vancouver, Calgary, Edmonton, Quebec City, Winnipeg and Hamilton.  - Mexico (, modern Nahuatl ), officially the United Mexican States, is a federal republic in the southern half of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatemala, Belize, and the Caribbean Sea; and to the east by the Gulf of Mexico. Covering almost two million square kilometers (over 760,000 sq mi), Mexico is the sixth largest country in the Americas by total area and the 13th largest independent nation in the world. With an estimated population of over 120 million, it is the eleventh most populous country and the most populous Spanish-speaking country in the world while being the second most populous country in Latin America. Mexico is a federation comprising 31 states and a federal district that is also its capital and most populous city. Other metropolises include Guadalajara, Monterrey, Puebla, Toluca, Tijuana and León.  - A safe house is, in a generic sense, a secret place for sanctuary or suitable to hide persons from the law, hostile actors or actions, or from retribution, threats or perceived danger. It may also be a metaphor.  - Nebraska City is a city and county seat of Otoe County, Nebraska, United States. As of the 2010 census, the city population was 7,289.  - Built in 1855 , the Mayhew Cabin and Historic Village in Nebraska City , Nebraska is the only Underground Railroad site in Nebraska officially recognized by the National Park Service . It is included among the sites of the National Underground Railroad Network to Freedom .  - The Underground Railroad was a network of secret routes and safe houses established in the United States during the early-to-mid 19th century, and used by African American slaves to escape into free states and Canada with the aid of abolitionists and allies who were sympathetic to their cause. The term is also applied to the abolitionists, both black and white, free and enslaved, who aided the fugitives. Various other routes led to Mexico or overseas. An earlier escape route running south toward Florida, then a Spanish possession, existed from the late 17th century until shortly after the American Revolution. However, the network now generally known as the Underground Railroad was formed in the early 1800s, and reached its height between 1850 and 1860. One estimate suggests that by 1850, 100,000 slaves had escaped via the "Railroad".  - Nebraska is a state that lies in both the Great Plains and the Midwestern United States. The state is bordered by South Dakota to the north, Iowa to the east and Missouri to the southeast, both across the Missouri River, Kansas to the south, Colorado to the southwest and Wyoming to the west. Its area is just over 77,220 sq mi (200,000 km) with almost 1.9 million people. Its state capital is Lincoln. Its largest city is Omaha, which is on the Missouri River.  - A census is the procedure of systematically acquiring and recording information about the members of a given population. It is a regularly occurring and official count of a particular population. The term is used mostly in connection with national population and housing censuses; other common censuses include agriculture, business, and traffic censuses. The United Nations defines the essential features of population and housing censuses as "individual enumeration, universality within a defined territory, simultaneity and defined periodicity", and recommends that population censuses be taken at least every 10 years. United Nations recommendations also cover census topics to be collected, official definitions, classifications and other useful information to co-ordinate international practice.  - A county seat is an administrative center, seat of government, or capital city of a county or civil parish. The term is used in the United States, Canada, Romania, China and Taiwan. In the United Kingdom and Ireland, county towns have a similar function.  - The National Park Service Organic Act (or simply "the Organic Act" within the National Park Service, conservationists, etc.) is a United States federal law that established the National Park Service (NPS), an agency of the United States Department of the Interior. The Act was signed into law on August 25, 1916, by President Woodrow Wilson, and is located in Title 16 of the United States Code.  - A national park is a park in use for conservation purposes. Often it is a reserve of natural, semi-natural, or developed land that a sovereign state declares or owns. Although individual nations designate their own national parks differently, there is a common idea: the conservation of 'wild nature' for posterity and as a symbol of national pride. An international organization, the International Union for Conservation of Nature (IUCN), and its World Commission on Protected Areas, has defined "National Park" as its "Category II" type of protected areas.  - The National Park Service (NPS) is an agency of the United States federal government that manages all U.S. national parks, many American national monuments, and other conservation and historical properties with various title designations. It was created on August 25, 1916, by Congress through the National Park Service Organic Act and is an agency of the United States Department of the Interior. The NPS is charged with a dual role of preserving the ecological and historical integrity of the places entrusted to its management while also making them available and accessible for public use and enjoyment.  - The United States Department of the Interior (DOI) is the United States federal executive department of the U.S. government responsible for the management and conservation of most federal land and natural resources, and the administration of programs relating to Native American, Alaska Natives, Native Hawaiians, territorial affairs, and insular areas of the United States. About 75% of federal public land is managed by the department, with most of the remainder managed by the Agriculture Department's United States Forest Service.    Given the information, choose the subject and object entities that have the relation of 'instance of'.
mayhew cabin , house