Identify the first widely used method for project planning: historically, the Bar chart (Gantt chart) preceded milestones, CPM, and PERT.

Introduction / Context:
Understanding the chronology of planning tools helps explain why different methods exist. Early tools emphasized simple visualization; later ones added logic and uncertainty analysis. This question asks which method came first historically.

Given Data / Assumptions:

• Options span bar charts, milestones, CPM, and PERT.
• We assume commonly accepted historical sequencing.

Concept / Approach:
Bar charts (Gantt charts) emerged in the 1910s–1920s. Milestone charts formalized milestone tracking later. CPM (1950s) introduced deterministic network logic and critical path; PERT (late 1950s) added probabilistic time estimates (to, tm, tp). Therefore, bar charts preceded the rest.

Step-by-Step Solution:
1) Place bar charts early (Gantt era).2) Recognize CPM/PERT were mid-20th-century innovations.3) Conclude Bar chart method is the earliest widespread planning method.

Verification / Alternative check:
Most project management histories trace a path: Gantt → milestones → CPM → PERT refinements for uncertainty.

Why Other Options Are Wrong:

• Milestone chart: Came after bar charts to highlight key dates.
• CPM: Developed in the 1950s (DuPont/Remington Rand).
• PERT: Late 1950s (U.S. Navy Polaris), after CPM.

Common Pitfalls:

• Assuming CPM/PERT predate simple charts due to their sophistication.
• Conflating milestone markers with the earlier bar visualization.

Final Answer:
Bar chart method.