Based on the available information, the boat ramp named Northwest Madrid Drive Polk City in Iowa is a public boat ramp. The width of the ramp is not specified, but it is likely to be wide enough for most standard-sized boats. The ramp services Saylorville Lake, a popular recreational lake in central Iowa.

According to the website of the U.S. Army Corps of Engineers, which manages Saylorville Lake, the lake is open to a wide range of watercraft, including power boats, sailboats, kayaks, canoes, and paddleboards. However, the website notes that some areas of the lake may be restricted to certain types of boats or activities, so it is important to check local regulations before launching.

Overall, it appears that the Northwest Madrid Drive boat ramp is a convenient and accessible spot for boaters and other water enthusiasts to access Saylorville Lake and enjoy all that the area has to offer.