Shirt Waisters were hugely popular dresses in the early 70s being such simple garments. The name says it all really, because these dresses were pretty much long, sleeveless or short sleeved shirts, which were cut just above the knee and buttoned all the way down. They were fitted at the waist and usually worn a little longer that the picture shows.
Occasionally you would add a belt but normally worn as seen and as you can see they came in some lovely designs.
Shirtwaisters were ideal dresses for the summer. They were versatile and could be as smart or as casual as you wanted and they suited all age groups.
There was a huge home dressmaking craze throughout the 70s. Lots of women and girls made their own clothes and the results could be surprisingly professional. Making your own clothes gave you the freedom to get exactly the right look, fit, and choose the material that you wanted. Because the Shirtwaister was so easy to make this type of dress was popular with the sewing machine brigade and often making a Shirtwaister dress was a school needlework project.
A female cousin of mine had to make a Shirtwaister dress for needlework classes at school and she had to unpick it so many times she never finished it. So not everyone was good at sewing in the 70s although it was much more popular than it is today.