Human operators collaborating to complete complex tasks, such as a team of emergency response operators, need to maintain a high level of situation awareness to appropriate-ly and quickly respond to critical changes. Even though automation can help manage complex tasks and rapidly update information, it may create confusion that negatively impacts operators' situation awareness, and result in sub-optimal decisions. To improve situation awareness in co-located environments on digital tabletop computers, we developed an interactive event timeline that enables exploration of historical system events, using a collaborative digital board game as a case study. We conducted a user study to examine two factors, placement of timelines for multiple users and location of awareness feedback, to understand their impact on situation awareness. The study revealed that interaction with the timeline was correlated with improved situation awareness, and that displaying feedback both on the game board and timeline was the most preferred.