Murr (Ps) are two sisters and two brothers in the Murr family. Their parents arranged for them to receive ownership of two lots the family used for recreation. The lots are adjacent, but the parents purchased them separately, put the title of one in the name of the family business, and later arranged for the transfer of the two lots, on different dates, to Ps. Wisconsin (D) rules prevent the use of lots as separate building sites unless they have at least one acre of land suitable for development. The rules also include a merger provision, which provides that adjacent lots under common ownership may not be “sold or developed as separate lots” if they do not meet the size requirement. Lot F was purchased in 1960 a small recreational cabin was built on it. In 1961, The parents transferred title to Lot F to the family plumbing company. In 1963, they purchased neighboring Lot E, which they held in their own names. The lots have the same topography. They each have less than one acre of land suitable for development. Even when combined, the lots’ buildable land area is only 0.98 acres due to the steep terrain. Lot F was conveyed to Ds in 1994, and Lot E was conveyed to them in 1995. Ps became interested in moving the cabin on Lot F to a different portion of the lot and selling Lot E to fund the project. They sought variances to allow the separate sale or use of the lots. The Board denied the requests, and the state courts affirmed in relevant part. The Wisconsin Court of Appeals agreed with the Board’s interpretation that the local ordinance “effectively merged” Lots E and F, so Ps “could only sell or build on the single larger lot.” Ps filed an action for a regulatory taking depriving them of “all, or practically all, of the use of Lot E because the lot cannot be sold or developed as a separate lot.” The Court granted summary judgment to D, explaining that Ps retained “several available options for the use and enjoyment of their property.” The Court of Appeals affirmed. The Court of Appeals rejected Ps’ request to analyze the effect of the regulations on Lot E only. Instead, the court held the takings analysis “properly focused” on the regulations’ effect “on Ps’ property as a whole.” Ps appealed.