This image starts a series of older black and white photos of Pine Lake State Park, located near Eldora, Iowa.
There is no description on the back of this card. This is apparently an image of Lower Pine Lake, with a boater in the middle of the lake and another just behind, near the island. The lake was formed by a dam constructed in 1922.
This image likely dates from the 1930s.

This image includes both of the main structures present at the Methodist Camp on Lake Okoboji during the 1940s. At right is the Tabernacle, which was a replacement for one built in 1915 and demolished by a tornado in 1926. In the distance is the Epworth Hall. The camp is used for Methodist families for summer recreation and religious studies.

The Tabernacle was rebuilt in 1927 and finally demolished in 2012. The Epworth Hall, built in 1928, is still present on the site. This image dates from the 1940s.

This image shows a couple of the private docks extending out from the Des Moines beach area of West Okoboji Lake. Tied up at the closer dock is an excellent example of a wooden pleasure boat from the 1940s.

Docks such as these  were commonly built by owners of lakefront property as well as being built and operated by resort and campground owners. This picture dates from the 1940s.

This is a view from the resort at Manhattan Beach, on the western shore of West Okoboji Lake in Iowa. The resort is still there, though much improved and expanded since this photo.

In the background, on the lake itself, is a tourist boat common on the lake then and now. This image dates from the 1940s.

Returning to the air again for a different view of the resort town and amusement park at Arnolds Park, Iowa, we see a smaller lake in the foreground, the isthmus of land beyond it where Arnolds Park is situated, and then the larger lake across the background of the photo.

Careful inspection of the image shows a notation on the near shoreline labelled “Oak Hill”. It is not clear what this signifies but it is in close proximity to a boat launch and pier, so it may be another public establishment.
This picture is clearly labeled as being from 1942.

Moving down to water level and focusing on the shoreline reveals the large pavilion building called the Roof Garden, a public hall available then and now for larger gatherings.

This building is now one of several facilities in place for events and performances as well as private rentals. The picture almost certainly dates from the 1940s.

This image, taken from along the shoreline south of Arnolds Park and looking to the northeast, highlights the amusement park that bordered the lake during this era.

The amusement park is still at this location and is thriving today. This image is marked with the date 1942.

This aerial photo shows the town of Arnolds Park as it borders on W. Okoboji Lake in Iowa. The town is in the extreme northwest corner of Iowa, and is closer to many cities in Minnesota than in Iowa.

This town forms much of the southeast shore of W. Okoboji Lake. This caption indicates this image was made in 1942.

This picture was taken from a vantage point that would put it just off the right edge of the previous picture. The same objects are present in the foreground and background.

In addition, the legend on the picture clearly states this is the Highway 71 route between the lakes, looking generally southwest. It is a habit of road constructors to put these barriers at the sides of bridges as they cross over water, but the difference in safety provided the barrier relative to the road immediately before and after is such as to make the barrier almost comical.
This card likely dates from the 1940s.

It is not clear exactly where this road is located in the Lake Okoboji area, but the fact that it is a long causeway between two bodies of water strongly implies it is the U.S. 71 Highway route between the two lakes.

The lakes are described as being distinct entities, but this navigable connection between them indicates they are now one body of water. This card likely dates from the 1940s.