Using the Census Bureau's API, you can retrieve quite a bit of information about counties, but you need to learn where it's stored. You can request up to 50 different variables in a single call, and you can ask for all counties in the US with one call.
To the census, "cities" are "places," and that includes things that you and I might think of as a city but ...
The U.S. Small Business Administration has an API that provides U.S. City and County Data.
This geographic names data set provides a "mashup" of URLs for official city and county government web sites and city and county location data from the USGS Geographic Names Information System (GNIS). GNIS data includes incorporated places, census designated areas, ...
I don't know specifics on how Zillow, etc acquired their data - other than assuming they (or 3rd party) obtains the data on a per county basis.
As cities/counties open up open data portals, this data will become more accessible to developers.
When searching these portals, you want to look for tax lots, property tax, or parcels.
A lot of these datasets are ...
I've been building an API for this called DemocracyMap. Probably the most relevant data resource for the basic details of city and county government is the Census of Governments: Government Integrated Directory which provides city/county name, address of gov office, phone number, etc. This in combination with Census Tiger boundary data will get you pretty ...
International organisations provide this kind of data. As you want to cover the whole World, have a look at organisations with the same geographical scope:
The World Bank has a database that covers a wide range of topics.
If you are more focussed on economic indicators, you can also have a look at the World Economic Outlook Database of the International ...
The data is in the Shapefile and the packaged dbf file. In QGIS, you can use the Attribute Table or Identify Feature tools to expose these attributes. Animated GIF below here: http://i.imgur.com/lSXp4Qr.gif
The 2010 Zip Code Tabulation Area, provided by the Census Bureau, in text format with the county number it is located in can be found here:
Converting the county number to its proper name can be done using this text database from the Census Bureau:
If you're looking for demographic information, the U.S. Census Bureau data could be helpful, especially the American Communities Survey. The QuickFacts section states that:
State and County QuickFacts provides frequently requested Census Bureau information at the national, state, county, and city level.
The primary long form Census data are only ...
The open elections project is trying to collect this type of information from official sources, though it isn't yet available.
This is commercially valuable information that typically comes with a licensing fee and can be problematic for republishing. "Election Data Services" is one of the usual sources for this data. Also see Dave Leip's political atlas ...
There is a Forbes article with an interactive graphic for county-to-country migration based on IRS tax records. Each county-to-county move must have at least 10 people, so as to protect privacy. The available years won't go back as far you ask.
The link given as a source is available from the Internet Archive.
But the ...
The link below is to the National Geospatial Agency (NGA) Geographic Name Server (GNS) for geographic features of Austrialia. The dataset has been converted to a linked CSV format and should be easy to parse. Your interest will be in records that are administrative divisions (NGA/GNS FCFC=A). The value of NGA/GNS DSG will tell you the type of administrative ...
The Census Geocoder can perform this lookup. This service also has an API that you can use. The documentation (PDF) might be helpful. For example, this query:
About import and export: TradeMap, a Swiss statistical tool providing indicators on:
They also have a directory of importing and exporting companies of more than 200 countries more than 5000 products.
Another economic indicator is the World Trade Organization Database, on ...
You'll have to mash things a little but this is available for free and should be fairly easy to setup:
Download the 2014 National Gazetteer, County Dataset, a tab delimited text file with 3200+ US counties, by state, ANSI code with Lat and Long.
Then, bang away at the USGS National Elevation Dataset Query Service for the elevation of a given lat/long.
census has longitude and latitude here by county:
elevation data is also here:
I was thinking you might be able to link the two together.
Here's some MISC resources to add to Kotebiya answer. Below is the USGS quick facts on elevations in the US. It has a list of the high/lowest for the largest 50 cities. Some other tables as well.
Maryland's GIS site has a list of high/low per county:
I suggest you search IPUMS, which has variables going back to 1850: https://usa.ipums.org/usa/index.shtml
I quickly searched and found that at least, personal income has been evaluated going back to 1940: https://usa.ipums.org/usa-action/variables/group?id=income
But a more detailed search might be even more fruitful.
I've found the most complete information of this information internationally (not just the U.S.) at statoids.com. One aspect of completeness is that Statoids explains the ambiguous issues.
For instance, your question seems straightforward enough, but Statoids notes: "The secondary administrative divisions of the United States are of several types. There ...
A word of caution about using the AP data made available through client sites such as Politico (or, for that matter, the New York Times): AP does make updates to its election results data, but most news organizations do not update their published data more than a few days after the election. So in most cases what you'll find in such feeds is incomplete data ...
Census has Metropolitan and Micropolitan Statistical Areas
as well as Combined Statistical Areas (CSA):
and CBSA (Core Based Statistical Areas):
Are you familiar with Python? The geopy library in combination with Open Street maps and Google maps does a tremendous jobs. It is very easy to analyze thousands of addresses as if you would put them in a google maps search box. The API gives you the political units such as country, state and city. If you like I can share a script that can handle excel ...
(After a while I have found some useful sources. I will answer my own question, so that future visitors to this site with the same question, have a starting point.)
Data 1940-1990 (from ICPSR):
Urbanization rate data for the earlier period can be obtained from the ICPSR 02896 data (see here). In particular, the datasets DS70 throughout DS78 and, in ...
Woods & Poole provide GDP for all U.S. counties. Unfortunately, they are a private, for-profit firm and consequently, the data has to be purchased. I will tell you that I purchased their entire database for all U.S. Metros and States and it is incredible! I would like to have had the database for all counties as well, but it was not necessary for my ...
I'm not sure you'll find exactly the data you want here because the data available looks quite difficult to explore but I would try the USA Counties Data File Downloads page of the US Census Bureau.
Some counties seems to give access to trade data too.
Hope it'll help ;)