**Core Concept**
The question is related to the history of water fluoridation, a public health measure aimed at preventing dental caries. Water fluoridation involves the addition of fluoride ions to community water supplies to promote oral health.

**Why the Correct Answer is Right**
The Grand Rapids study, conducted in collaboration with Muskegon, was the first controlled study on water fluoridation. It was initiated in 1945 and concluded in 1955. The study involved two similar cities in Michigan: Grand Rapids, which received fluoridated water, and Muskegon, which did not. This design allowed researchers to compare the incidence of dental caries between the two cities, providing valuable insights into the efficacy of water fluoridation.

**Why Each Wrong Option is Incorrect**
* **Option B:** Newberg & Kingston are not associated with any notable water fluoridation studies in the medical literature.
* **Option C:** Brantford & Sarnia are cities in Canada, and while they have been involved in various public health initiatives, they are not linked to the first study on water fluoridation.
* **Option D:** Evanston & Park are not recognized as being involved in any significant water fluoridation studies.

**Clinical Pearl / High-Yield Fact**
The Grand Rapids study demonstrated a significant reduction in dental caries among children living in areas with fluoridated water supplies, paving the way for the widespread adoption of water fluoridation as a public health measure.

**✓ Correct Answer: A. Grand rapids (Michigan) & Muskegon**