|Location|Name of mill and grid reference|Type|Maps|First mention or built|Last mention or demise|
|---|---|---|---|---|---|
|Chesfield||Post||1318|1372|
|Chesfield|Chesfield Park|Titt iron wind engine||1896||
|Cheshunt|TL 317 036|Post||1843|Demolished c. 1860|
|Cheshunt|Goff's Oak Mill TL 317 036|Tower||c. 1860|Demolished 1953|
|Cheshunt|Turner's Hill Mill TL 363 023||1822|1822|1861|
|Chipperfield|TL 037 014|Post||1594|1594|
|Chipperfield|TL 037 014|Smock|1822|1822|1881, gone by 1896|
|Chipping|Approximately TL 350 319|Post|1720 1728|1720|1728|
|Clothall|Approximately TL 264 326|Post||1370|1370|
|Codicote|Codicote Heath Approximately TL 206 185|Smock||1841|1855, gone by 1881|
|Colney Heath|Colney Heath Mill TL 205 055|Tower||1854|Windmill World|
|Cottered||Post||1581|1581|
|Cromer||||1192|1576|
|Cromer|Cromer Mill TL 304 286|Post|1720 1728 1749 1766 1800 1822|1720|Windmill World|
|Croxley Green|Croxley Green Mill TQ 067 953|Tower||c. 1860|Windmill World|

Question: how many locations have or had at least 2 windmills?
Answer: 4