Route 185 was commissioned in 1932 as a 6.18-mile route from US 44 in West Hartford to Route 10 in Simsbury. Its original route, from south to north:

• N. Main St. (part of today's Route 218) from US 44 to Simsbury Rd.
• Simsbury Rd. (today's Route 185 as well) to Route 10

In 1936, Route 218 was added, but it did not immediately take over the N. Main St. segment of Route 185. Instead, Route 218 southbound turned left at the 218/185 intersection, to follow Simsbury Road back to Route 189.

One of the many recommendations of the 1961 Route Reclassification was that routes 218 and 185 should simply cross each other; their segments south and east of their intersection were swapped in 1963.

Some older maps showed Route 185 continuing south along Main Street to Farmington Avenue (former Route 4); but I haven't seen this reflected in 1940s or early '50s highway logs.

In 1973, the state announced plans to realign about a mile of Route 185, from East Weatogue Street to the Bloomfield town line. What was eventually done, in the mid-1980s: a minor widening, along with a long passing lane on the eastbound side.