Missouri, a state near the geographical center of the United States, has three distinct physiographic divisions:
The boundary between the northern plains and the Ozark region follows the Missouri river from its mouth at St. Louis to Columbia. This also corresponds to the southernmost extent of glaciation during the Pre-Illinoian Stage which destroyed the remnant plateau to the north but left the ancient landforms to the south unaltered. The Ozark boundary runs southwestward from there towards Joplin at the southeast corner of Kansas. The boundary between the Ozark and lowland regions runs southwest from Cape Girardeau on the Mississippi River to the Arkansas border just southwest of Poplar Bluff.
Springfield is the third largest city in the State of Missouri and the county seat of Greene County. According to the 2010 census data, the population was 159,498, an increase of 5.2% since the 2000 census. The Springfield Metropolitan Area, population 436,712, includes the counties of Christian, Dallas, Greene, Polk and Webster. Springfield's nickname is the Queen City of the Ozarks and is known as the Birthplace of Route 66 as well as the home of several universities including Missouri State University.
Juglans nigra, the eastern black walnut, a species of flowering tree in the walnut family, Juglandaceae, is native to eastern North America. It grows mostly in riparian zones, from southern Ontario, west to southeast South Dakota, south to Georgia, northern Florida and southwest to central Texas. Isolated wild trees in the upper Ottawa Valley may be an isolated native population or may have derived from planted trees.
The black walnut is a large deciduous tree attaining heights of 30–40 m (98–130 ft). Under forest competition, it develops a tall, clear bole; the open-grown form has a short bole and broad crown. The bark is grey-black and deeply furrowed. The pith of the twigs contains air spaces. The leaves are alternate, 30–60 cm long, odd-pinnate with 15–23 leaflets, with the largest leaflets located in the center, 7–10 cm long and 2–3 cm broad. The male flowers are in drooping catkins 8–10 cm long, the female flowers are terminal, in clusters of two to five, ripening during the autumn into a fruit (nut) with a brownish-green, semifleshy husk and a brown, corrugated nut. The whole fruit, including the husk, falls in October; the seed is relatively small and very hard. The tree tends to crop more heavily in alternate years. Fruiting may begin when the tree is 4–6 years old, however large crops take 20 years. Total lifespan of J. nigra is about 130 years.
The native flora of the United States includes about 17,000 species of vascular plants, plus tens of thousands of additional species of other plants and plant-like organisms such as algae, lichens and other fungi, and mosses. About 3,800 additional non-native species of vascular plants are recorded as established outside of cultivation in the U.S., as well as a much smaller number of non-native non-vascular plants and plant relatives. The United States possesses one of the most diverse temperate floras in the world, comparable only to that of China.]citation needed[
Several biogeographic factors contribute to the richness and diversity of the U.S. flora. While most of the United States has a temperate climate, Alaska has vast arctic areas, the southernmost part of Florida is subtropical to tropical, Hawaii is fully tropical (including high mountains), and alpine summits are present on many western mountains, as well as a few in the Northeast. The U.S. coastline borders three oceans: The Atlantic (and Gulf of Mexico), the Arctic, and the Pacific. Finally, the U.S. shares long borders with Canada and Mexico, and is relatively close to the Bahamas, Cuba and other Caribbean islands, and easternmost Asia.
The United States is a country in the Northern Hemisphere, Western Hemisphere, and the Eastern Hemisphere. It consists of forty-eight contiguous states in North America, Alaska, a peninsula which forms the northwestern most part of North America, and Hawaii, an archipelago in the Pacific Ocean. There are several United States territories in the Pacific and Caribbean. The term "United States", when used in the geographical sense, means the continental United States, Alaska, Hawaii, Puerto Rico, Guam, and the Virgin Islands of the United States. The country shares land borders with Canada and Mexico and maritime (water) borders with Russia, Cuba, and the Bahamas in addition to Canada and Mexico.