The Hazardous Materials Table is found at 49 CFR Part 172 – view the entire table at one of the links below. This table identifies the four digit UN Code, proper labeling, packaging and shipping requirements for over 3,000 materials regulated by DOT as Hazardous Materials.
Government Printing Office link (pdf format): https://www.govinfo.gov/content/pkg/CFR-2008-title49-vol2/pdf/CFR-2008-title49-vol2-sec172-101.pdf
DOT historically provided a compilation of the table in spreadsheet format, available for download from the PHMSA website. While this file is no longer available from DOT, a 2013 version can be downloaded here. Use caution when using this file as it does not reflect the current HMT.