Technical Abstract: Climate has been of primary concern from the beginning of agricultural and natural resources research. Early in the 20th century, climatology and agronomy evolved as separate disciplines, focusing primarily on production agriculture and crop adaptation to new regions. Key concepts developed include thermal units and water use efficiency, which remain important today. In the mid 20th century, the integrated discipline of agroclimatology developed, along with agricultural meteorology and environmental physics. Numerous papers related to the discipline were named as Citation Classics, as theoretical understanding evolved rapidly. Spectral properties of plants and soils were identified that provide the basis of today's remote sensing technologies. Commercialization of scientific instrumentation enhanced our ability to efficiently collect data using standardized methods. Partnerships between the private-sector and public-sector researchers greatly advanced the research capacity. Later in the 20th century, research focus shifted toward integration of knowledge across disciplines into crop growth and agronomic models. Remote sensing provided capacity to extend theoretical understanding of the land-atmosphere interface and gain practical understanding of regional scale processes. Environmental issues became increasingly important across all aspects of agricultural research. In the early 21st century, recognition of earth as a system along with inter-related human systems is driving research and political agendas. There is a pressing need to change our data-rich to an information-rich environment. The emerging cyberinformatics field along with natural resource and agricultural system models are providing capacity to apply climate information to assessments and decision support related to water supply, agricultural production, environmental management, and many other issues. Solutions to today's problems require that agroclimatologists work collaboratively with broad interdisciplinary and multi-sectoral teams. While needs have never been greater, availability of training in agroclimatology is diminishing, as fewer universities maintain critical mass required to offer advance degrees in agroclimatology. It will be increasingly important that agrclimatology attract top students and provide training and practical experience in conducting integrated systems research, communications, and team skills.