Green’s Dictionary of Slang

ranch n.

(US) a brothel.

1863		Geelong Advertiser 15 May 3/6: [A] whole army of (brazen courtesans and ‘painted Jezebels’ has invaded the city [...] The places where they have congregated have received the name [...] ‘Ranches,’ a word that in Texas signifies an enclosure for cattle. The ‘Ranches’ of Madame This or That are as openly conduced as the hotels or boarding-houses.
1881		Nat. Police Gaz. (NY) 8 Oct. 2/3: Officer Boyles [...] recognized the description as that of a girl he had seen [...] at Madame Thornton’s ranch, on Main street.

In phrases

go to the ranch (v.) [the ranch style ‘homosexual healing centres’ advocated by anti-gay campaigner Anita Bryant]

(US gay) to go crazy.

1999

Gaymart.com Queer Sl. in the Gay 90s 🌐 The Ranch – As in ‘ She’s going to the ranch’. A way of saying someone is going crazy.