Weed invasion is a current threat to productivity in croplands and biodiversity conservation in natural ecosystems. Missouri ranks second in cow-calf numbers in the United States and its pastureland has experienced invasion of various plant species. Sericea Lespedeza (Lespedeza cuneata) is one of the invasive weeds and is becoming a serious threat to pasturelands in this state. The in-situ field survey in these vast pastures is time consuming and often impossible because of accessibility. Typical aerial survey is also difficult to detect sericea because the plant is of similar size and color as natural grass and thus cannot be discriminated in a common aerial color photo. This study used an airborne hyperspectral image (AISA at the CALMAT, University of Nebraska) to map sericea and its invasiveness in a public grass field and a private hayfield in Mid-Missouri. The maximal 1^st-order derivative in red-near infrared region was derived to separate sericea from natural grass. With a simple threshold approach, sericea in various sizes were identified in the study area. It was also found that the variation of maximal 1^st-order derivative of sericea patches was log-linearly related to sericea volume, a measure of intensity of sericea invasiveness in three dimensions. The 2-m multi-spectral aerial photos from the National Agriculture Image Program (NAIP) were also used to test how much information was lost when data was reduced from hyper- to multi-spectral images. The quantitative distribution of sericea in this study could serve as a first step in alerting landowners and the general public about the seriousness of sericea invasion in pasturelands in Missouri.