The two most important words in Houston's history are 'oil' and 'cattle.' But the city's spectacular growth would never have happened without two others: 'air' and 'conditioning.' Until the 1930s, Houston was a sleepy regional center with a population under 100,000. Thus you'll find relatively few historic buildings here. Once air-conditioning became available on a widespread basis, the population jumped; by 1960 it numbered nearly a million.
From the 1970s through 1990s, the city's fortunes followed the price per barrel of oil: boom, then bust. The area's business base diversified to include the medical services, high-tech and space industries. Throughout the 2000s, Houston's economic growth continued, attracting a diverse, multicultural population. Over 200,000 New Orleans residents resettled in Houston after Huricane Katrina in 2005, which has added even more to the strong Creole and Cajun influences in the city.
In 2009 Annise Parker was elected as the first openly lesbian mayor of a large US city. She served three terms until 2016 when term limits prevented her from running again (she'd been hugely popular). She was replaced by Sylvester Turner, a longtime African American politician.