Answer

Refer to the NYU Business Library's Economic & Statistics page:

Global Financial Data offers downloadable financial data series.

On the Business Library's company page:

Search in Mergent Archives: select CRB from the left menu to access the Mergent Commodity Yearbook with data starting from 1939.

Search in Bloomberg:

• Type BMAP and hit the <GO> key to plot mines and mining sites (for gold, coal, metals, etc.) as points on a map.
• Type CRR and hit the <GO> key to rank commodity indexes.
• Refer to the Bloomberg guide for more information. 
• Library Bloomberg stations are located on the 5th floor of Bobst Library, NYU AD and NYU Shanghai Libraries.

Explore government tools:

• UNCTADstat (United Nations Conference on Trade and Development)  provides free market commodity prices (including indices) starting from 1960. Select Data Center > Commodity Prices.
• USGS (United States Geological Survey) Commodity Statistics and Information reports on nonfuel mineral commodities.
• The USDA (United States Department of Agriculture) Economic, Statistics and Market Information System offers
• The World Bank publishes data and analyses of Commodity Markets and Global Economic Prospects. agricultural commodity market data and outlooks.