The document discusses the development of a crowdsourcing tool called CrowdSkippr that predicts crowd sizes at specific locations on future dates using historical data. It extracts data on photos taken from Flickr and temperatures from NOAA to train a gradient boosting regression model. The model predicts crowds will be lowest on certain days based on factors like day of week, holidays, temperature. Validation shows the predicted best days typically have crowd sizes within 4.6% of actual best days. The tool helps users choose dates for trips that minimize crowds.