Mapping in ArcGIS: Choropleth and Proportional Symbol Mapping

Goal:

The goal of this project was to become more familiar with mapping functions in ArcGIS by creating a county-level graduated color map depicting a chosen theme, in this case Whites as a Percentage of the 2012 Population in the United States and a county-level proportional symbol map of the Number of Females per County in 2012.  The current demographic information as of 2012 was used to learn about the different types of census data as well. 

Methods:

To complete these maps, a data frame for the contiguous United States, Hawaii, and Alaska in ArcGIS were created with states and county outlines.  then, a scale, north arrow, legend, title, source, and projection information was put onto the map according to the rules of visual hierarchy.  In the graduated color map's attribute table, the percentage of the white population was selected and then a graduated color map was created from the data.  For the proportional symbol map, the number of females was selected and sized appropriately for the map scale. 

Results:

 The graduated color map shows the percentage of the population that self-identifies as caucasian.  The data was separated using the natural break method and expressed as a percentage.  the map shows a higher concentration of predominantly white counties located in the Midwest and Eastern United States along the northern border.  the northern portion of Alaska, Hawaii and a strip of land running from Virginia down through Mississippi have lower percentages of caucasians. Alaska and Hawaii have lower rates of caucasians because these areas were the last to be added to the United States and they lacked the initial surge of immigrants that the contiguous United States had. The northern part of the Midwest and Eastern United States has predominantly caucasian populations because many European immigrants settled there.  The concentrated strip of counties that are low in caucasians coincide with the center of the former slave plantations so these counties still hold substantial numbers of African Americans.  Lower California also shows smaller percentages of caucasians, and this could be caused by Mexican immigrants moving into these counties.  Figure 1 shows the final product of the proportional symbol map.

Figure 1. Graduated Color Map of Whites as a Percentage of the 2012 Population in the United States.

 The proportional symbol map shows the number of females per county in the United States.  The highest numbers of females were located in the eastern half of the United States, with the exception of a few higher areas in California and the Washington/Oregon area.  When the numbers of females are compared to the cities with a population of greater than 100,000 people, a strong correlation exists.  It is also interesting to note that the female population drastically decreases at the 90th meridian.  There are several factors that could contribute to this phenomenon, such as the lack of cities in the west besides the west coast, and the rural lifestyle common in the Western United States.  Alaska also has a very low female population, but their population is low for both males and females.  The lack of females in places like Alaska and the western United States could also be attributed to the types of jobs in different areas.  The west typically has more outside work that requires manual labor, which historically has had low female numbers of employment. Figure 2 shows the final product for the proportional symbol map. 

Figure 2. Proportional Symbol Map of the Number of Females per County in 2012. 

Sources:

ESRI