Soil-bentonite (SB) cutoff walls are commonly employed in the US to control groundwater flow and subsurface contaminant migration. In these applications, both the short-term (as built) integrity of the barrier and the potential for degradation in the integrity of the barrier over time are of critical importance. Although many laboratory studies have been conducted to investigate the hydraulic performance of SB cutoff walls and various factors affecting this performance, field investigations are scarce. With support from the National Science Foundation, a 194 m long, 7 m deep, and 0.9 m wide SB cutoff wall has been designed, constructed, and instrumented to serve as a long-term field research site for investigating the in-situ properties and behavior of SB backfill. This paper provides an overview of the project, instrumentation details, and representative post-construction testing and monitoring results. The results presented herein include index and hydraulic properties of the as-mixed SB backfill measured in the laboratory using the grab samples collected during construction, and monitoring data (i.e., inclinometer surveys, backfill settlement monitoring, and backfill state of stress measurements) collected during the construction period and for the first 120 days after construction. The results indicate that the wall was well constructed and successfully instrumented to yield insightful information regarding the development of stresses and deformations in the backfill. The backfill continues to undergo secondary compression and load transfer to the adjacent formation, resulting in continued decreases in total stress. As expected, total stresses in the wall are considerably lower than would be predicted by assuming a geostatic stress distribution in the backfill. Effective stresses in the backfill are increasing gradually over time as excess pore pressures dissipate, but remain very low (≤10 kPa) after 120 days and are likely to remain low. Inclinometer results show that progressively inward displacements continue to occur adjacent to the wall, indicating progressive lateral squeezing of the backfill. None of the stresses, deformations, or pore pressures have reached equilibrium at the time of this writing, and monitoring will continue in the months and years ahead. Future work will focus on evaluating existing and newly developed models for predicting stress and strain development in SB cutoff walls with comparisons made to the measured field data; in-situ testing and sampling to investigate variability and changes in the hydraulic and strength properties of the backfill as a function of location, depth, scale, and time; and evaluation of electrical resistivity as a viable geophysical technique to non-destructively identify the presence of defects in the wall.