Many zip codes in the northeastern part of the United States have zip codes that start with a zero. We collect locations and store them in our CSV file with these zeros intact. If you look at any of the CSV files in their raw format, such as with Notepad or another text editor, you will see the zeros correctly.

The problem occurs when you open the file in Microsoft Excel or another spreadsheet program. Excel does not recognize the values as zip codes, just as regular numbers, so it cuts off the leading zero. In order to fix this, highlight the zip code column, right click, and select "Format Cells" There should be a category called "Special", under which there is a format titled "Zip Code". Select this format type and click OK.

This is the process for the latest couple of versions of Excel, but there should be similar methods for other spreadsheet software.