The effect of row spacing and plant population on soybean [Glycine max L. (Merr.)] growth and yield development in the Upper Midwest is not well understood. Our objective was to determine how light interception, biomass accumulation, and yield components change in response to different plant distributions. Studies were established at three locations in Iowa for two years with two row widths (38 cm and 76 cm) and four plant populations (185000, 309000, 432000, and 556000 plants ha^-1. Growth analysis data was collected from only one location. Averaged across locations, grain yield increased 470 kg ha^-1 as row spacing decreased and no yield response was observed for increased plant population. Canopy biomass was 14% greater and light interception was 17% greater for the narrow row spacing and resulted in increased crop growth rate 84 days after emergence. Plant populations of 185000 plants ha^-1 did not intercept as much light as higher populations and crop growth rate was reduced up to the R2 growth stage. Higher plant populations reduced the number of pods plant^-1, seeds plant^-1, and seed mass of branch seeds compared to lower populations; however, yield was maintained by a greater number of plants contributing to seed number m^-2. At wide row spacing and low plant population branch pods contributed to a greater percentage of seed number m^-2. No individual yield component could be identified as the cause for the yield reduction caused by wide row spacing, rather there were small reductions for all yield components and plants m^-2 that combined to reduce yield. The data indicates that decreased row spacing can be an important management tool to increase yield whereas changing plant population will not be an effective method to increase yield.