A hurricane in 1875 killed about 400 people in Indianola, followed by another hurricane in 1886 that destroyed the town. These events allowed Galveston to take over as the chief port city. The 1900 Galveston hurricane subsequently devastated that city, killing about 8,000 people or possibly as many as 12,000. This makes it the deadliest natural disaster in U.S. history. In 2017, Hurricane Harvey made landfall in Rockport as a Category 4 Hurricane, causing significant damage there. The storm stalled over land for a very long time, allowing it to drop unprecedented amounts of rain over the Greater Houston area and surrounding counties. The result was widespread and catastrophic flooding that inundated hundreds of thousands of homes. Harvey ultimately became the costliest hurricane worldwide, causing an estimated $198.6 billion in damage, surpassing the cost of Hurricane Katrina. Other devastating Texas hurricanes include the 1915 Galveston hurricane, Hurricane Audrey in 1957 which killed more than 600 people, Hurricane Carla in 1961, Hurricane Beulah in 1967, Hurricane Alicia in 1983, Hurricane Rita in 2005, and Hurricane Ike in 2008. Tropical storms have also caused their share of damage: Allison in 1989 and again during 2001, Claudette in 1979, and Tropical Storm Imelda in 2019. There is no substantial physical barrier between Texas and the polar region. Although it is unusual, it is possible for arctic or polar air masses to penetrate Texas, as occurred during the February 13–17, 2021 North American winter storm. Usually, prevailing winds in North America will push polar air masses to the southeast before they reach Texas. Because such intrusions are rare, and, perhaps, unexpected, they may result in crises such as the 2021 Texas power crisis. Greenhouse gases , Texas emitted the most greenhouse gases in the U.S., almost twice the amount of California, the second-most polluting state. the state emits about of carbon dioxide annually. As an independent state, Texas would rank as the world's seventh-largest producer of greenhouse gases. Causes of the state's vast greenhouse gas emissions include the state's large number of coal power plants and the state's refining and manufacturing industries. In 2010, there were 2,553 "emission events" which poured of contaminants into the Texas sky. Administrative divisions The state has three cities with populations exceeding one million: Houston, San Antonio, and Dallas. These three rank among the 10 most populous cities of the United States. As of 2020, six Texas cities had