Located on the Arkansas River in northeastern Oklahoma, Tulsa is the second largest city in the state. In the 1830s the Creek Indians began to settle in this part of Indian Territory and in 1898 Tulsa was incorporated as a city. Tulsa remained a small town for a couple of year. However in 1901 oil was discovered off the banks of the Arkansas River. Then in 1905, just south of Tulsa, one of the largest and richest oil wells was discovered in present day Glenn Pool. The Glenn Pool discovery led to an economic boom and gave Tulsa the nickname "The Oil Capital of the World" for a portion of the 20th Century. During this time Tulsa population soared from just 1,300 in 1900 to over 140,000 in the 1930's. Oil barons began constructing their own city that was reaching into the sky. As a result of the oil boom, Tulsa has become known for its many fine examples of Art Deco architecture, which many consider to be one of the best examples in the United States. Some examples of the architecture can be seen in the Mid-Continent Tower and the Philtower . Tulsa began to slow some during the oil bust of the late 20th Century but has remained a strong and viable city. Today Tulsa is home to some of the largest companies in the fields of natural gas, telecommunications and aerospace. One such company is Williams. Williams has their headquarters located in the BOK Tower which once was the tallest building in the "Five Plains States" Even though Tulsa has expanded into other industries, oil is still the driving force of Tulsa's economy. The city is laid out in the green, tree rich hills of Green Country. Tulsa is always considered one of the most beautiful cities in the United States as well being consistently ranked as one of the most livable.