Townhomes are common in cities and densely populated neighborhoods. Townhouses are tall and narrow homes designed to make the most out of vertical space without too much of a yard or garden area.

Homes are considered townhouses when they:

• Share one or two walls with adjacent homes
• Have their own entrances
• Are built with multiple floors to maximize vertical space
• Often share a similar style to their neighbors’ homes and may operate under an HOA

Townhouses can be built to mimic other architecture styles, like Italianate and Greek Revival, while maintaining the condensed, vertical floor plan.

Federal-style homes became popular after the American Revolution and were a refined upgrade to the popular Georgian house style. They have the same recurring shape and symmetry as other Colonial house styles, but their delicate ornamentation sets them apart.

Federal Colonial homes often feature:

• A layout built around a central hall
• An elliptical fanlight and two flanking lights (windows) around the door
• Paladin or tripartite windows

The elliptical fanlights and paladin windows are key distinguishing features from Georgian-style homes.

Gothic Revival architecture grew in the mid-19th century and was one of the early styles of Victorian-era homes. The Gothic Revival style takes influence from Medieval Europe and was designed as a country home. Architects believed the asymmetrical design and ornamentation complemented the nature of rural America.

Gothic Revival homes can be identified by their:

• Pointed arch in windows, doors, and decoration
• Elaborate wood trim vergeboards and bargeboards
• Steeply pitched roofs and front-facing gables
• Towers and turrets resembling medieval castles

Gothic Revival architecture was a popular style for schools and churches as well as rural homes.

The National Academy of Sciences (NAS) is a United States nonprofit, non-governmental organization. NAS is part of the National Academies of Sciences, Engineering, and Medicine, along with the National Academy of Engineering (NAE) and the National Academy of Medicine (NAM).

As a national academy, new members of the organization are elected annually by current members, based on their distinguished and continuing achievements in original research. Election to the National Academy is one of the highest honors in the scientific field. Members of the National Academy of Sciences serve pro bono as "advisers to the nation" on science, engineering, and medicine. The group holds a congressional charter under Title 36 of the United States Code.

Founded in 1863 as a result of an Act of Congress that was approved by Abraham Lincoln, the NAS is charged with "providing independent, objective advice to the nation on matters related to science and technology. … to provide scientific advice to the government 'whenever called upon' by any government department."[2]

The Academy receives no compensation from the government for its services.[3]

The Academy currently has 2,984 members and international members. Existing members elect new members for life. Up to 120 members are elected every year; up to 30 foreign citizens may be elected as international members annually. The election process begins with a formal nomination, followed by a vetting period, and culminates in a final ballot at the Academy's annual meeting in April each year. Members are affiliated with a section -- a specific scientific field -- in one of six so-called "classes": (1) Physical and Mathematical Sciences; (2) Biological Sciences; (3) Engineering and Applied Sciences; (4) Biomedical Sciences; (5) Behavioral and Social Sciences; and (6) Applied Biological, Agricultural, and Environmental Sciences.[6] Since its founding, the Academy has elected 6,457 members. Harvard University is associated with the most members (329), some 5% of the all-time total. The top ten institutions, half of which are Ivy League universities, account for nearly 28% of all members ever elected.[11]

The United States has 63 national parks, which are Congressionally-designated protected areas operated by the National Park Service, an agency of the Department of the Interior.[1] National parks are designated for their natural beauty, unique geological features, diverse ecosystems, and recreational opportunities. While legislatively all units of the National Park System are considered equal with the same mission, national parks are generally larger and more of a destination, and hunting and extractive activities are prohibited.[2] National monuments, on the other hand, are also frequently protected for their historical or archaeological significance. Eight national parks (including six in Alaska) are paired with a national preserve, areas with different levels of protection that are administered together but considered separate units and whose areas are not included in the figures below. The 423 units of the National Park System can be broadly referred to as national parks, but most have other formal designations.[3]

A bill creating the first national park, Yellowstone, was signed into law by President Ulysses S. Grant in 1872, followed by Mackinac National Park in 1875 (decommissioned in 1895), and then Rock Creek Park (later merged into National Capital Parks), Sequoia and Yosemite in 1890. The Organic Act of 1916 created the National Park Service "to conserve the scenery and the natural and historic objects and wildlife therein, and to provide for the enjoyment of the same in such manner and by such means as will leave them unimpaired for the enjoyment of future generations."[4] Many current national parks had been previously protected as national monuments by the president under the Antiquities Act or as other designations created by Congress before being redesignated by Congress; the newest national park is New River Gorge, previously a National River, and the most recent entirely new park is National Park of American Samoa. A few former national parks are no longer designated as such, or have been disbanded. Fourteen national parks are designated UNESCO World Heritage Sites (WHS),[5] and 21 national parks are named UNESCO Biosphere Reserves (BR),[6] with eight national parks in both programs.

Thirty states have national parks, as do the territories of American Samoa and the U.S. Virgin Islands. The state with the most national parks is California with nine, followed by Alaska with eight, Utah with five, and Colorado with four. The largest national park is Wrangell–St. Elias in Alaska: at over 8 million acres (32,375 km2), it is larger than each of the nine smallest states. The next three largest parks are also in Alaska. The smallest park is Gateway Arch National Park, Missouri, at 192.83 acres (0.7804 km2). The total area protected by national parks is approximately 52.2 million acres (211,000 km2), for an average of 829 thousand acres (3,350 km2) but a median of only 208 thousand acres (840 km2).[7]

The national parks set a visitation record in 2017, with more than 84 million visitors and set a further record in 2018 with a 0.1% increase.[8][9] Great Smoky Mountains National Park in North Carolina and Tennessee has been the most-visited park since 1944,[10] and had over 14 million visitors in 2021.[11] In contrast, only about 7,000 people visited the remote Gates of the Arctic National Park and Preserve in Alaska in 2021.

Contemporary homes resemble the modern homes of the mid-20th century with a renewed emphasis on sustainability. Current contemporary styles are rooted in minimalism, which you can see in these key features:

• Asymmetrical exterior
• Clean lines
• Open floor plan layout
• Geometry highlighted in its structure
• Sustainable building materials and features

Contemporary homes aim to find beauty in a simple and appealing design with ties to nature and more warmth than modern home styles offer.

Colonial-style houses are simple rectangular homes that became popular in the 1600s as colonists settled the East Coast. These homes have many variations due to the fact that new communities all over the world built Colonial-style homes to suit their culture.

British Colonial style is the most common and recognizable Colonial home. Its key features include:

• A side-gabled roof
• Two floors
• A centered front door
• Symmetrical windows on either side of the door

The rectangular shape and interest in symmetry are seen in other Colonial house styles, too. Materials and decorative features can vary by region, as some Colonial houses sport brick exteriors and ornate trim, while others showcase shingle siding and simple shutters.

These are also some of the cheapest types of houses to build.

Mediterranean home styles are made of stucco, so they’re most common in warm climate states like Arizona and California. These homes grew in popularity in the 1920s and ‘30s after being featured as homes for the rich and famous on the silver screen.

Mediterranean-style homes include Spanish and Italian architectural elements. These key features make them easy to spot:

• Stucco walls painted white or brown
• Classic red tile roofs
• Arched doorways and windows
• Ornamentation including wrought iron, heavy doors, and decorative tiles

Mediterranean homes still carry the feelings of class and luxury they were built with over 100 years ago, with an added element of history and charm.

The French Colonial house style can be seen around the world and has significant variety among its sub-styles.

French Colonial houses have the same symmetry as other Colonial homes with these distinct features:

• Dormer windows, including one centered above the door
• External stairs to enter higher floors
• Iron stairs and balconies
• Slightly raised basements to support the floor

French Colonial houses are most similar to Spanish Colonial houses and easily identified by their elaborate iron balconies, stairs, and entrances.