Each month, the National Climatic Data Center provides an archive of one minute interval data from the ASOS sites in the United States. Unfortunately, the data format of this information is brutal to work with. Fortunately for you, the IEM processes this information and provides it for download here. The archive is available up until: 01 Sep 2018. There is a different interface to download the routine hourly observations from this network and for sites over the entire globe.