Sampling hard-to-reach populations can be difficult with traditional survey methods. Challenges arise because sampling frames are typically unknown, and individuals can be wary of authority or afraid of being identified by the stigmatized or illegal nature of their behaviors. A contemporary solution is respondent-driven sampling (RDS), a survey method spearheaded by Heckathorn (1997) that utilizes links in underlying social networks to create branching referral chains of respondents. Obtaining samples for the target population is heavily impacted by RDS parameters, such as field site and the location of the initial respondents (“seeds”). However, the relationship between the RDS parameters and the eventual sample is not yet thoroughly understood. This paper reviews spatial patterns in two RDS samples from Chicago and New Orleans to determine the relative importance of seed and field site location, as well as assess the impact of physical barriers.