King's Highway 406 (pronounced "four-oh-six"), commonly referred to as Highway 406, is a 400-series highway in the Canadian province of Ontario. The primary north-south route through the central portion of the Niagara Peninsula, Highway 406 connects Welland, Thorold and downtown St. Catharines to the Queen Elizabeth Way (QEW). Construction of Highway 406 began in 1963. The first section opened between St. Davids Road and Geneva Street on December 7, 1965, followed by a southward extension to Beaverdams Road in late 1969. The route was later extended south as a super two to Merritt Road where it became Highway 58. In 1977, construction began to connect the freeway with the QEW; this was completed in late 1984. Construction on the route resumed in 1987, connecting the route with East Main Street in Welland, completed in 1995. In 2009 construction resumed on the highway to expand the remaining two-lane sections to a four-lane divided freeway, with the existing route becoming the southbound lanes of the new freeway. The southern terminus in Welland was converted to a roundabout while the remaining at-grade intersections were rebuilt as interchanges. Route description From 1987 until 2015, Highway 406 was unique as the only 400-series highway with two lane sections and with an at-grade rail crossing. The highway is heavily travelled within St. Catharines, but volumes drop considerably south of the city. The speed limit on Highway 406 varies from to . It is patrolled by the Ontario Provincial Police. The 406 designation begins at East Main Street in Welland at a roundabout immediately west of East Main Street Tunnel beneath the Welland Canal. From here the now-four-lane divided road veers northeast and travels parallel to the canal. Two golf courses separate the canal. As the highway passes to the west of them, it jogs to the west and crosses a Trillium Railway spur (formerly at-grade, now over the railway), and meets Daimler Parkway and Woodlawn Road at a newly constructed interchange. Soon after, it crosses the Welland River and then the former channel of the canal, which was replaced by the current Welland By-Pass in the 1970s. The highway curves to the northwest as it passes through thick forest, and meets another newly built interchange with Merritt Road (formerly Highway 58), which as of 2009 was being rebuilt as a grade-separated interchange. After this, it returns to its northward orientation and passes the final former at-grade