Editing Mackinac Bridge (section)

===Formal planning===
In 1923, the state legislature ordered the State Highway Department to establish ferry service across the strait. More and more people used ferries to cross the straits each year, and as they did, the movement to build a bridge increased. [[Chase Osborn]], a former governor, wrote:

{{blockquote|Michigan is unifying itself, and a magnificent new route through Michigan to Lake Superior and the Northwest United States is developing, via the Straits of Mackinac. It cannot continue to grow as it ought with clumsy and inadequate ferries for any portion of the year.<ref>{{harvp|Rubin|1958|p=13}}.</ref>}}

By 1928, the ferry service had become so popular and so expensive to operate that Governor [[Fred W. Green]] ordered the department to study the feasibility of building a bridge across the strait. The department deemed the idea feasible, estimating the cost at $30&nbsp;million (equivalent to ${{formatprice|{{Inflation|US-GDP|30000000|1928}}}} in {{Inflation-year|US-GDP}}{{Inflation-fn|US-GDP}}).

In 1934, the Michigan Legislature created the ''Mackinac Straits Bridge Authority'' to explore possible methods of constructing and funding the proposed bridge.<ref name=":0">{{cite book |author = Board of Engineers |date = January 10, 1950 |title = Proposed Mackinac Straits Bridge Preliminary Report |url = https://www.michigan.gov/-/media/Project/Websites/egle/Documents/Programs/OGMD/Catalog/12/Proposed-Prelim-Report.pdf |publisher = Mackinac Bridge Authority |access-date = June 20, 2024 }}</ref> The Legislature authorized the Authority to seek financing for the project. In the mid-1930s, during the Great Depression, when numerous infrastructure projects received federal aid, the Authority twice attempted to obtain federal funds for the project but was unsuccessful. The [[United States Army Corps of Engineers]] and President [[Franklin D. Roosevelt]] endorsed the project but Congress never appropriated funds. Between 1936 and 1940, the Authority selected a route for the bridge based on preliminary studies. Borings were made for a detailed [[geology|geological]] study of the route.<ref name=":0" />

The preliminary plans for the bridge featured a three-lane roadway, a railroad crossing on the underdeck of the span, and a center-anchorage double-suspension bridge configuration similar to the design of the San Francisco–Oakland Bay Bridge. Because this would have required sinking an anchorage pier in the deepest area of the Straits, the practicality of this design may have been questionable.{{Citation needed|date=September 2011}} A concrete causeway, approximately {{convert|4000|ft|m|0}}, extending from the northern shore, was constructed in shallow water from 1939 to 1941. However, a unique engineering challenge was created by the tremendous forces that operate against the base of the bridge, because the lakes freeze during the winter, causing large icebergs to place enormous stress on the bridge.{{citation needed|date=October 2020}}

At that time, with funding for the project still uncertain, further work was put on hold because of the outbreak of [[World War II]]. The ''Mackinac Straits Bridge Authority'' was abolished by the state legislature in 1947, but the same body created a new [[Mackinac Bridge Authority]] three years later in 1950. In June 1950, engineers were retained for the project. By then, it was reported that cars queuing for the ferry at Mackinaw City did not reach St. Ignace until five hours later, and the typical capacity of 460 vehicles per hour could not match the estimated 1,600 for a bridge.<ref>{{harvp|Rubin|1958|p=23}}.</ref>

After a report by the engineers in January 1951,<ref>{{cite book |type = Report |url = https://www.michigan.gov/documents/deq/Proposed_Prelim_Report_opt_306071_7.pdf |title = Proposed Mackinac Straits Bridge Preliminary Report |access-date = April 15, 2013 |last = Ammann |first = Othmar |author-link = Othmar Ammann |date = January 10, 1951 }}</ref> the state legislature authorized the sale of $85&nbsp;million (equivalent to ${{formatprice|{{Inflation|US-GDP|85000000|1952}}}} in {{Inflation-year|US-GDP}}{{Inflation-fn|US-GDP}}) in bonds for bridge construction on April 30, 1952. However, a weak bond market in 1953 forced a delay of more than a year before the bonds could be issued.