Text Size

American Landscapes - Maricopa County, Ariz., Submitted by Michelle Fuller
Arizona's capital of Phoenix and neighboring towns in Maricopa County have undergone a major population boom in the last 40 years. The effects of this boom are seen in everything from the expansion of town and cities to an increased demand for fresh water. Michelle Fuller from Gilbert wrote asking to see these changes to the landscape; most visible in this series of images is how city streets and development are now covering the land that previously was used for agriculture.

Timelapse of Phoenix, in Maricopa County, Ariz., from 1972-2011. In these Landsat images, vegetation (that is, plant growth) appears red. (Credit: NASA's Goddard Space Flight Center/USGS)
› Download this video in broadcast quality from NASA Goddard's Scientific Visualization Studio

map of continental United States with Maricopa, Ariz., labeled Central Arizona's "Valley of the Sun" encompasses most of Maricopa County and has long attracted people because of the perceived health benefits of its desert environment: low humidity and warm winters. Arizona's capital of Phoenix and neighboring towns grew during the first half of the 20th century, but the Second World War and post-war era saw increased urbanization as thousands of service personnel, especially air crews, came to the valley to trainin the mostly cloud free environment and settled permanently in the Phoenix area.

After the war, the electronics and aerospace engineering industries, along with the existing drivers of the economy, agriculture and state government, thrived in the area during the post-war era as more and more people came to call Maricopa County home. Another major factor increasing the region’s urban growth was the advent of the widespread air conditioning.Two years before the launch of the first Landsat satellite in 1972, Maricopa County had grown substantially to approximately 960,000 people and it was ranked 24th among U.S. counties nationally for population.

In the Landsat montage of annual images, the developed land covers show up as purple gray as light is mostly reflected back into space from the growing amounts of impervious surfaces like of streets and roads, rooftops, parking lots, and industrial areas. Irrigated farmland shows up mainly as red geometrically shaped areas. The dominant desert shrublands appear muted gray indicating mostly vegetated but dry conditions. In the early 1970s, the developed land covers in the early 1970s were more centrally concentrated. Chandler is a separate area of urban land located between Phoenix South Mountain Park on the left and Williams Air Force Base on the right. Another outlier of developed land on the northwest side of the metropolitan area during the early 1970s was Sun City, a prototypical example of a community focused on retiree living.

By 1985, Maricopa County’s population had passed 1.5 million people and new sources of water had been found. During its earlier history, metropolitan Phoenix had used mostly local and nearby water sources, such as from the Salt River Valley and the mountainous Roosevelt Reservoir located north of the urbanized area. In 1985, water from the Colorado River on the California-Arizona border began being pumped east as part of the Central Arizona Project (CAP), bringing additional resources both to Maricopa County and to the Tucson area. Lake Pleasant shows up about this time just north of the urban area, the main holding reservoir for the CAP water.

Landsat animation showing Phoenix in 1972 and 2011 In this animated pair of images from 1972 and 2011, impervious surfaces (roads and other pavement in urban areas) are shown in red. (Credit: USGS EROS Data Center)
› 1972 image
› 2011 image

Urbanization continued and by the time of the 2000 census, Maricopa County had reached a milestone with over three million people, becoming the fourth most populated single county in the U.S.. By 2000, less green areas of irrigated agriculture are visible in the Landsat imagery even though in 2005 farming continued to still use 46 percent of the water in the Phoenix. The U.S. Census of Agriculture indicates about a quarter million acres (approximately 1,000 square kilometers) decrease in total cropland in Maricopa County between 1974 and 2007. Farming is still a significant land use within the county, especially further out form the urbanized area such around Gila Bend and in the Harquahala Valley. The number of dairy cows in Maricopa County actually increased between 1974 and 2007, from approximately 50,000 to more than 95,000 and irrigated land used for hay production stayed nearly constant at around 80,000 acres (325 square kilometers).

Data from the 2010 Census of Population shows that Maricopa County was still ranked fourth in overall population (3,817,000). Arizona was the second leading state for growth between 2000 and 2005, much of it centered in Maricopa County, with the great majority of the population change coming from net in-migration, otherwise known as more people moving in than leaving.

Related Links

› American Landscapes bibliography

Roger Auch, Research Geographer
USGS EROS Data Center