This dataset and documentation contains detailed information of the iTEM Open Database, a harmonized transport data set of historical values, 1970 - 2018. It aims to create transparency through two key features: Open-Data: Assembling a comprehensive collection of publicly-available transportation data Open-Code: All code and documentation will be publicly accessible and open for modification and extension. https://github.com/transportenergy The iTEM Open Database is comprised of individual datasets collected from public sources. Each dataset is downloaded, cleaned, and harmonised to the common region and technology definitions defined by the iTEM consortium https://transportenergy.org. For each dataset, we describe the name of the dataset, the web link to the original source, the web link to the cleaning script (in python), variables, and explain the data cleaning steps (which explains the data cleaning script in plain English).